commenting properly and docstring added

xga/generate/esass/spec.py

@@ -554,23 +554,50 @@ def _append_spec_info(evt_list):
 
     return sources_cmds, stack, execute, num_cores, sources_types, sources_paths, sources_extras, disable_progress
 
-def _ext_map_creation():
-
-        im = source.get_combined_images(lo_en=Quantity(0.2, 'keV'), hi_en=Quantity(10.0, 'keV'), 
+def _ext_map_creation(source, outer_radii, dest_dir, combined_obs):
+        """
+        Internal function to make ext_map images for extended sources, so that they can be corrected
+        for vignetting/ effective area correctly when spectra are generated in esass. This function
+        returns a path to the created ext_map that can be input into the EXTMAP argument in the 
+        srctool command.
+
+        :param BaseSource source: The source to generate an extmap for.
+        :param astropy.units.Quantity outer_radii: outer radius of the mask to be applied.
+        :param str dest_dir: The destination directory for the extmap to be written to.
+        :param bool combined_obs: Indictating whether or not to use combined obs for this source.
+
+        :return: The path of the created extmap.
+        :rtype: str
+        """
+        # Depending on combined obs, we need to retrieve either a combined image or a single image
+        if combined_obs:
+            im = source.get_combined_images(lo_en=Quantity(0.2, 'keV'), hi_en=Quantity(10.0, 'keV'), 
+                                        telescope='erosita')
+        else:
+            im = source.get_images(lo_en=Quantity(0.2, 'keV'), hi_en=Quantity(10.0, 'keV'), 
                                         telescope='erosita')
 
-        mask = source.get_custom_mask(outer_radii[src_ind], telescope='erosita')
+        # Making the mask from the outer radii of the spectra, as parsed by the user into the 
+        # srctool_spectrum command
+        mask = source.get_custom_mask(outer_radii, telescope='erosita')
 
-        im_data = img.data
+        im_data = im.data
         masked_im = mask*im_data
+
+        # just trying to conserve memory
         del(mask)
         del(im_data)
+
+        # Writing the the wcs and masked image into a fits file
         im_header = im.radec_wcs.to_header()
         prim_hdu = PrimaryHDU()
         img_hdu = ImageHDU(data=masked_im, header=im_header)
         extensions = [prim_hdu, img_hdu]
         hdulist = HDUList(extensions)
-        hdulist.writeto(dest_dir + 'extmap.fits')
+        extmap_path = dest_dir + "extmap.fits"
+        hdulist.writeto(extmap_path)
+
+        return extmap_path
 
 # # TODO fix this function to use XGA in built function and I still need to debug
 # TODO DAVID - Actually don't think that this is necessary anymore