Get foreign keys info

    :type ins: sqlalchemy.orm.mapper.Mapper
    :rtype: list[SaForeignkeyDoc]

def _model_foreign(ins):
    """ Get foreign keys info

    :type ins: sqlalchemy.orm.mapper.Mapper
    :rtype: list[SaForeignkeyDoc]
    """
    fks = []
    for t in ins.tables:
        fks.extend([
            SaForeignkeyDoc(
                key=fk.column.key,
                target=fk.target_fullname,
                onupdate=fk.onupdate,
                ondelete=fk.ondelete
            )
            for fk in t.foreign_keys])
    return fks