code: def _filter_pb(field_or_unary):
      
      if isinstance(field_or_unary, query_pb2.StructuredQuery.FieldFilter):
          return query_pb2.StructuredQuery.Filter(field_filter=field_or_unary)
      elif isinstance(field_or_unary, query_pb2.StructuredQuery.UnaryFilter):
          return query_pb2.StructuredQuery.Filter(unary_filter=field_or_unary)
      else:
          raise ValueError("Unexpected filter type", type(field_or_unary), field_or_unary)
docs: Convert a specific protobuf filter to the generic filter type.
  
      Args:
          field_or_unary (Union[google.cloud.proto.firestore.v1beta1.\
              query_pb2.StructuredQuery.FieldFilter, google.cloud.proto.\
              firestore.v1beta1.query_pb2.StructuredQuery.FieldFilter]): A
              field or unary filter to convert to a generic filter.
  
      Returns:
          google.cloud.firestore_v1beta1.types.\
          StructuredQuery.Filter: A "generic" filter.
  
      Raises:
          ValueError: If ``field_or_unary`` is not a field or unary filter.