code: def get_connection(self, from_obj, to_obj):
          
          self._validate_ctypes(from_obj, to_obj)
          try:
              return self.connections.get(from_pk=from_obj.pk, to_pk=to_obj.pk)
          except Connection.DoesNotExist:
              return None
docs: Returns a ``Connection`` instance for the given objects or ``None`` if
          there's no connection.