code: def _build_implicit_prefetches(
          self,
          model,
          prefetches,
          requirements
      ):
          
  
          for source, remainder in six.iteritems(requirements):
              if not remainder or isinstance(remainder, six.string_types):
                  # no further requirements to prefetch
                  continue
  
              related_field = get_model_field(model, source)
              related_model = get_related_model(related_field)
  
              queryset = self._build_implicit_queryset(
                  related_model,
                  remainder
              ) if related_model else None
  
              prefetches[source] = self._create_prefetch(
                  source,
                  queryset
              )
  
          return prefetches
docs: Build a prefetch dictionary based on internal requirements.