:type table: Table instance

    :type cols: strings or Column instances

    """

    __migrate_visit_name__ = 'migrate_primary_key_constraint'

    def __init__(self, *cols, **kwargs):

        colnames, table = self._normalize_columns(cols)

        table = kwargs.pop('table', table)

        super(PrimaryKeyConstraint, self).__init__(*colnames, **kwargs)

        if table is not None:

            self._set_parent(table)

    def autoname(self):

        """Mimic the database's automatic constraint names"""

        return "%s_pkey" % self.table.name

class ForeignKeyConstraint(ConstraintChangeset, schema.ForeignKeyConstraint):

    """Construct ForeignKeyConstraint

    Migrate's additional parameters:

    :param columns: Columns in constraint

    :param table: If columns are passed as strings, this kw is required

    :type table: Table instance

    :type columns: list of strings or Column instances

    :type refcolumns: list of strings or Column instances

    """

    __migrate_visit_name__ = 'migrate_foreign_key_constraint'

    def __init__(self, columns, refcolumns, *args, **kwargs):

        colnames, table = self._normalize_columns(columns)

        table = kwargs.pop('table', table)

        refcolnames, reftable = self._normalize_columns(refcolumns,

                                                        table_name=True)

        super(ForeignKeyConstraint, self).__init__(

            colnames, refcolnames, *args,**kwargs

        )

        if table is not None:

            self._set_parent(table)

    @property

    def referenced(self):

        return [e.column for e in self.elements]

    @property