code: def _avro_schema(read_session):
      
      json_schema = json.loads(read_session.avro_schema.schema)
      column_names = tuple((field["name"] for field in json_schema["fields"]))
      return fastavro.parse_schema(json_schema), column_names
docs: Extract and parse Avro schema from a read session.
  
      Args:
          read_session ( \
              ~google.cloud.bigquery_storage_v1beta1.types.ReadSession \
          ):
              The read session associated with this read rows stream. This
              contains the schema, which is required to parse the data
              blocks.
  
      Returns:
          Tuple[fastavro.schema, Tuple[str]]:
              A parsed Avro schema, using :func:`fastavro.schema.parse_schema`
              and the column names for a read session.