docs: def _filter_by_simple_schema(self, qs, lookup, sublookup, value, schema):
          """
          Filters given entity queryset by an attribute which is linked to given
          schema and has given value in the field for schema's datatype.
          """
          value_lookup = 'attrs__value_%s' % schema.datatype
          if sublookup:
              value_lookup = '%s__%s' % (value_lookup, sublookup)
          return {
              'attrs__schema': schema,
              str(value_lookup): value
          }