'Commits pending updates to Amazon DynamoDB.
:type expected_value: dict
:param expected_value: A dictionary of name/value pairs that
you expect.  This dictionary should have name/value pairs
where the name is the name of the attribute and the value is
either the value you are expecting or False if you expect
the attribute not to exist.
:type return_values: str
:param return_values: Controls the return of attribute name/value pairs
before they were updated. Possible values are: None, \'ALL_OLD\',
\'UPDATED_OLD\', \'ALL_NEW\' or \'UPDATED_NEW\'. If \'ALL_OLD\' is
specified and the item is overwritten, the content of the old item
is returned. If \'ALL_NEW\' is specified, then all the attributes of
the new version of the item are returned. If \'UPDATED_NEW\' is
specified, the new versions of only the updated attributes are
returned.'

def save(self, expected_value=None, return_values=None):

    return self.table.layer2.update_item(self, expected_value, return_values)
