update series to use middle image

generic/models.py

@@ -42,6 +42,7 @@ from django.forms.models import model_to_dict
 
 
 def findMiddle(input_list):
+    """Returns the middle element of a list"""
     middle = float(len(input_list)) / 2
     if middle % 2 != 0:
         return input_list[int(middle - 0.5)]