code: def _init_metadata_table():
      
      _metadata_table = sqlalchemy.Table(
          'metadata', _METADATA,
          sqlalchemy.Column(
              'job_id', sqlalchemy.ForeignKey("jobs.job_id", ondelete="CASCADE"),
              nullable=False, primary_key=True),
          sqlalchemy.Column('key', sqlalchemy.UnicodeText, primary_key=True),
          sqlalchemy.Column('value', sqlalchemy.UnicodeText, index=True),
          sqlalchemy.Column('type', sqlalchemy.UnicodeText),
          )
      return _metadata_table
docs: Initialise the "metadata" table in the db.