diff --git a/chapter_9/Pipfile.lock b/chapter_9/Pipfile.lock
index dba8d2a..edcc2dd 100644
--- a/chapter_9/Pipfile.lock
+++ b/chapter_9/Pipfile.lock
@@ -3,19 +3,6 @@
         "hash": {
             "sha256": "0ace1a8e4cedd21b8e198d372e762cd8da980d7ec9cfcefae1d4a2ab3e3d97e7"
         },
-        "host-environment-markers": {
-            "implementation_name": "cpython",
-            "implementation_version": "3.6.5",
-            "os_name": "posix",
-            "platform_machine": "x86_64",
-            "platform_python_implementation": "CPython",
-            "platform_release": "17.7.0",
-            "platform_system": "Darwin",
-            "platform_version": "Darwin Kernel Version 17.7.0: Thu Jun 21 22:53:14 PDT 2018; root:xnu-4570.71.2~1/RELEASE_X86_64",
-            "python_full_version": "3.6.5",
-            "python_version": "3.6",
-            "sys_platform": "darwin"
-        },
         "pipfile-spec": 6,
         "requires": {},
         "sources": [
@@ -29,62 +16,64 @@
     "default": {
         "pymongo": {
             "hashes": [
+                "sha256:075686718e64483b95abf224317925687742e810dbf95d5750c8fb36cf88a5ec",
+                "sha256:08dea6dbff33363419af7af3bf2e9a373ff71eb22833dd7063f9b953f09a0bdf",
+                "sha256:0949110db76eb1b54cecfc0c0f8468a8b9a7fd42ba23fd0d4a37d97e0b4ca203",
                 "sha256:0c31a39f440801cc8603547ccaacf4cb1f02b81af6ba656621c13677b27f4426",
+                "sha256:1dcde7e63d50c957fc377a6cdf56c90635015a3a41b894be96d9421458608706",
+                "sha256:1e10b3fda5677d360440ebd12a1185944dc81d9ea9acf0c6b0681013b3fb9bc2",
                 "sha256:1f59440b993666a417ba1954cfb1b7fb11cb4dea1a1d2777897009f688d000ee",
-                "sha256:aec4ea43a1b8e9782246a259410f66692f2d3aa0f03c54477e506193b0781cb6",
-                "sha256:daedcfbf3b24b2b687e35b33252a9315425c2dd06a085a36906d516135bdd60e",
-                "sha256:966d987975aa3b4cfcdf1495930ff6ecb152fafe8e544e40633e41b24ca3e1c5",
-                "sha256:8e939dfa7d16609b99eb4d1fd2fc74f7a90f4fd0aaf31d611822daaff456236f",
-                "sha256:c8669f96277f140797e0ff99f80bd706271674942672a38ed694e2bfa66f3900",
-                "sha256:ce7c91463ad21ac72fc795188292b01c8366cf625e2d1e5ed473ce127b844f60",
+                "sha256:2b5a3806d9f656c14e9d9b693a344fc5684fdd045155594be0c505c6e9410a94",
+                "sha256:34bb6b32969677d7f6a9694945899c5c9324d93094874b5fe9c0a4aa10323a49",
+                "sha256:3a7ed4a2ad7abc4bc29a5ec181e23bd370ba4003767260519f825db96f1daf63",
+                "sha256:457faf75fc9e8c25625240436508c4e482f977a31363a84a9a25fabb4b8a2194",
                 "sha256:4a14e2d7c2c0e07b5affcfbfc5c395d767f94bb1a822934a41a3b5371cde1458",
-                "sha256:562c353079e8ce7e2ad611fd7436a72f5df97be72bca59ae9ebf789a724afd5c",
-                "sha256:52999666ad01de885653e1f74a86c2a6520d1004afec475180bebf3d7393a8fc",
-                "sha256:d776d8d47884e6ad39ff8a301f1ae6b7d2186f209218cf024f43334dbba79c64",
                 "sha256:4cb50541225208b37786fdb0de632e475c4f00ec4792579df551ef48d6999d69",
-                "sha256:ccf00549efaf6f8d5b35b654beb9aed2b788a5b33b05606eb818ddaa4e924ea3",
-                "sha256:1e10b3fda5677d360440ebd12a1185944dc81d9ea9acf0c6b0681013b3fb9bc2",
-                "sha256:b752088a2f819f163d11dfdbbe627b27eef9d8478c7e57d42c5e7c600fee434e",
-                "sha256:08dea6dbff33363419af7af3bf2e9a373ff71eb22833dd7063f9b953f09a0bdf",
-                "sha256:ffe94f9d17800610dda5282d7f6facfc216d79a93dd728a03d2f21cff3af7cc6",
-                "sha256:b73f889f032fbef05863f5056b46468a8262ae83628898e20b10bbbb79a3617e",
-                "sha256:0949110db76eb1b54cecfc0c0f8468a8b9a7fd42ba23fd0d4a37d97e0b4ca203",
+                "sha256:52999666ad01de885653e1f74a86c2a6520d1004afec475180bebf3d7393a8fc",
+                "sha256:562c353079e8ce7e2ad611fd7436a72f5df97be72bca59ae9ebf789a724afd5c",
                 "sha256:5ce2a71f473f4703daa8d6c61a00b35ce625a7f5015b4371e3af728dafca296a",
+                "sha256:6192bf37933d16d5348e9d7ca6f3b2a45fbafe110ac77460e67dc856913d1b2f",
                 "sha256:6613e633676168a4500e5e6bb6e3e64d3fdb96d2dc472eb4b99235fb4141adb1",
-                "sha256:2b5a3806d9f656c14e9d9b693a344fc5684fdd045155594be0c505c6e9410a94",
-                "sha256:8fa4303e1f50d9f0c8f2f7833b5a370a94d19d41449def62b34ae072126b4dfd",
-                "sha256:e7ad1ec621db2c5ad47924f63561f75abfd4fff669c62c8cc99c169c90432f59",
-                "sha256:f2d9eb92b26600ae6e8092f66da4bcede1b61a647c9080d6b44c148aff3a8ea4",
-                "sha256:f16c7b6b98bc400d180f05e65e2236ef4ee9d71f3815280558582670e1e67536",
-                "sha256:dab0f63841aebb2b421fadb31f3c7eef27898f21274a8e5b45c4f2bccb40f9ed",
+                "sha256:69d757cc9786e1417cc44230073c82e490f8f5c4a71299de7dba8fbce7193f8f",
+                "sha256:75183c8336e25b4b879dc8fc8d13a585abb5e0042d0ddbd4b54fb36c11f849bf",
                 "sha256:8330406f294df118399c721f80979f2516447bcc73e4262826687872c864751e",
+                "sha256:847c8ce15a1b5634c7a62732899f339d168a443115cd9bc37c52d75fb362bca1",
+                "sha256:8c1436e9b65fd2c0c46141cef108cae8cd303c0d233af7c0e0de18b3c59c6dcf",
+                "sha256:8e939dfa7d16609b99eb4d1fd2fc74f7a90f4fd0aaf31d611822daaff456236f",
+                "sha256:8fa4303e1f50d9f0c8f2f7833b5a370a94d19d41449def62b34ae072126b4dfd",
                 "sha256:8fae0e607d954aa5f2acfbb2be79f7359521b2b9a4458a995c5baf48868bc4b4",
-                "sha256:075686718e64483b95abf224317925687742e810dbf95d5750c8fb36cf88a5ec",
-                "sha256:69d757cc9786e1417cc44230073c82e490f8f5c4a71299de7dba8fbce7193f8f",
-                "sha256:e750ceff90998e53c0f4b6a3080ec1ccf5aa264e290996b963a59ab6a782d5a5",
+                "sha256:966d987975aa3b4cfcdf1495930ff6ecb152fafe8e544e40633e41b24ca3e1c5",
+                "sha256:aec4ea43a1b8e9782246a259410f66692f2d3aa0f03c54477e506193b0781cb6",
                 "sha256:b1f6cac26ed5aaf811e6310d5829506eee7f0c5f113fd5a5c2bd4c584d6a994f",
-                "sha256:75183c8336e25b4b879dc8fc8d13a585abb5e0042d0ddbd4b54fb36c11f849bf",
-                "sha256:1dcde7e63d50c957fc377a6cdf56c90635015a3a41b894be96d9421458608706",
-                "sha256:34bb6b32969677d7f6a9694945899c5c9324d93094874b5fe9c0a4aa10323a49",
-                "sha256:e4b348c2f51cb1bd75a31f3fc53eee59975ff7349def12f8f6e2d6cc198e849a",
+                "sha256:b73f889f032fbef05863f5056b46468a8262ae83628898e20b10bbbb79a3617e",
+                "sha256:b752088a2f819f163d11dfdbbe627b27eef9d8478c7e57d42c5e7c600fee434e",
+                "sha256:bf9e9bcb2f4a8fa1cc5e956c92a9c5f8a6cf5d4f81e2e8a696ff5af5626d66b6",
+                "sha256:c8669f96277f140797e0ff99f80bd706271674942672a38ed694e2bfa66f3900",
+                "sha256:ccf00549efaf6f8d5b35b654beb9aed2b788a5b33b05606eb818ddaa4e924ea3",
+                "sha256:ce7c91463ad21ac72fc795188292b01c8366cf625e2d1e5ed473ce127b844f60",
                 "sha256:d3e9c3ef66c99e11e432a1f1cf51dbe82b9ced646e8fff3309e52d4318561de5",
-                "sha256:457faf75fc9e8c25625240436508c4e482f977a31363a84a9a25fabb4b8a2194",
+                "sha256:d776d8d47884e6ad39ff8a301f1ae6b7d2186f209218cf024f43334dbba79c64",
+                "sha256:dab0f63841aebb2b421fadb31f3c7eef27898f21274a8e5b45c4f2bccb40f9ed",
+                "sha256:daedcfbf3b24b2b687e35b33252a9315425c2dd06a085a36906d516135bdd60e",
+                "sha256:e4b348c2f51cb1bd75a31f3fc53eee59975ff7349def12f8f6e2d6cc198e849a",
+                "sha256:e750ceff90998e53c0f4b6a3080ec1ccf5aa264e290996b963a59ab6a782d5a5",
+                "sha256:e7ad1ec621db2c5ad47924f63561f75abfd4fff669c62c8cc99c169c90432f59",
                 "sha256:e9a6b224362bbdfc3e18fcb03c449422bf3a826b7365a77fcd863bcdef020b7c",
-                "sha256:3a7ed4a2ad7abc4bc29a5ec181e23bd370ba4003767260519f825db96f1daf63",
-                "sha256:8c1436e9b65fd2c0c46141cef108cae8cd303c0d233af7c0e0de18b3c59c6dcf",
-                "sha256:847c8ce15a1b5634c7a62732899f339d168a443115cd9bc37c52d75fb362bca1",
-                "sha256:bf9e9bcb2f4a8fa1cc5e956c92a9c5f8a6cf5d4f81e2e8a696ff5af5626d66b6",
-                "sha256:6192bf37933d16d5348e9d7ca6f3b2a45fbafe110ac77460e67dc856913d1b2f",
-                "sha256:f14fb6c4058772a0d74d82874d3b89d7264d89b4ed7fa0413ea0ef8112b268b9"
+                "sha256:f14fb6c4058772a0d74d82874d3b89d7264d89b4ed7fa0413ea0ef8112b268b9",
+                "sha256:f16c7b6b98bc400d180f05e65e2236ef4ee9d71f3815280558582670e1e67536",
+                "sha256:f2d9eb92b26600ae6e8092f66da4bcede1b61a647c9080d6b44c148aff3a8ea4",
+                "sha256:ffe94f9d17800610dda5282d7f6facfc216d79a93dd728a03d2f21cff3af7cc6"
             ],
+            "index": "pypi",
             "version": "==3.7.1"
         },
         "redis": {
             "hashes": [
-                "sha256:8a1900a9f2a0a44ecf6e8b5eb3e967a9909dfed219ad66df094f27f7d6f330fb",
-                "sha256:a22ca993cea2962dbb588f9f30d0015ac4afcc45bee27d3978c0dbe9e97c6c0f"
+                "sha256:56732e156fe31801c4f43396bd3ca0c2a7f6f83d7936798531b9848d103381aa",
+                "sha256:7df17a0a2b72a4c8895b462dd07616c51b1dcb48fdd7ecb7b6f4bf39ecb2e94e"
             ],
-            "version": "==2.10.6"
+            "index": "pypi",
+            "version": "==4.5.3"
         }
     },
     "develop": {}