Fix import order

Author: henhuy

src/oemof/solph/_models.py

@@ -14,10 +14,10 @@
 SPDX-License-Identifier: MIT
 
 """
+import itertools
 import logging
 import warnings
 from logging import getLogger
-import itertools
 
 from oemof.tools import debugging
 from pyomo import environ as po

src/oemof/solph/processing.py

@@ -14,20 +14,20 @@
 SPDX-License-Identifier: MIT
 
 """
-import sys
-from itertools import groupby, accumulate
 import operator
+import sys
+from itertools import accumulate
+from itertools import groupby
 
 import numpy as np
 import pandas as pd
 from oemof.network.network import Entity
 from pyomo.core.base.piecewise import IndexedPiecewise
 from pyomo.core.base.var import Var
 
-from .helpers import flatten
-
 from oemof.solph.components._generic_storage import GenericStorage
 
+from .helpers import flatten
 
 PERIOD_INDEXES = ("invest", "total", "old", "old_end", "old_exo")