'Add a \'dependency\' for this Table.
This is another Table object which must be created
first before this one can, or dropped after this one.
Usually, dependencies between tables are determined via
ForeignKey objects.   However, for other situations that
create dependencies outside of foreign keys (rules, inheriting),
this method can manually establish such a link.'

def add_is_dependent_on(self, table):

    self._extra_dependencies.add(table)
