class ImplicitForeignKeyConstraint(ForeignKeyConstraint):

    def __init__(self, columns, refcolumns, primary_key=None, **kwargs):

        super(ImplicitForeignKeyConstraint, self).__init__(
                columns, refcolumns, **kwargs)
        self.primary_key_flag = primary_key

    def _set_parent(self, table):
        referenced_table = table.metadata.tables[
                    self.elements[0].target_fullname.split('.')[0]]
        for column in self.columns:
            new_column = getattr(referenced_table.c, column).copy()
            if self.primary_key_flag is not None:
                new_column.primary_key = self.primary_key_flag
            table.append_column(new_column)
        super(ImplicitForeignKeyConstraint, self)._set_parent(table)