'Load an SDF from S3
Using this method will result in documents added through
:func:`add` and :func:`delete` being ignored.
:type key_obj: :class:`boto.s3.key.Key`
:param key_obj: An S3 key which contains an SDF'

def add_sdf_from_s3(self, key_obj):

    self._sdf = key_obj.get_contents_as_string()
