<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _init_metadata_table():
 """Initialise the "metadata" table in the db."""

    _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