'Drop all tables stored in this metadata.
Conditional by default, will not attempt to drop tables not present in
the target database.
:param bind:
A :class:`.Connectable` used to access the
database; if None, uses the existing bind on this ``MetaData``, if
any.
:param tables:
Optional list of ``Table`` objects, which is a subset of the
total tables in the ``MetaData`` (others are ignored).
:param checkfirst:
Defaults to True, only issue DROPs for tables confirmed to be
present in the target database.'

def drop_all(self, bind=None, tables=None, checkfirst=True):

    if (bind is None):
        bind = _bind_or_error(self)
    bind._run_visitor(ddl.SchemaDropper, self, checkfirst=checkfirst, tables=tables)
