'Gets a Cursor given its byte string serialized form.
The serialized form of a cursor may change in a non-backwards compatible
way. In this case cursors must be regenerated from a new Query request.
Args:
cursor: A serialized cursor as returned by .to_bytes.
Returns:
A Cursor.
Raises:
datastore_errors.BadValueError if the cursor argument does not represent a
serialized cursor.'

@staticmethod
def from_bytes(cursor):

    return Cursor(_cursor_bytes=cursor)
