human
Complete this python program:
def encode_index_pb(pb):
assistant
#Here is the Python code you requested.

    """Returns an encoded protocol buffer.
    Args:
    pb: The protocol buffer to encode.
    Returns:
    An encoded protocol buffer.
    """
    def _encode_path(pb):
        '    Takes    a    protocol    buffer    and    returns    the    encoded    path.    '
        path = []
        for e in pb.element_list():
            if e.has_name():
                key_id = e.name()
            elif e.has_id():
                key_id = str(e.id()).zfill(ID_KEY_LENGTH)
            path.append('{0}:{1}'.format(e.type(), key_id))
        val = dbconstants.KIND_SEPARATOR.join(path)
        val += dbconstants.KIND_SEPARATOR
        return val
    if (isinstance(pb, entity_pb.PropertyValue) and pb.has_uservalue()):
        userval = entity_pb.PropertyValue()
        userval.mutable_uservalue().set_email(pb.uservalue().email())
        userval.mutable_uservalue().set_auth_domain('')
        userval.mutable_uservalue().set_gaiaid(0)
        pb = userval
    def remove_nulls(value):
        '    Remove    null    values    from    a    given    string    and    byte    stuff    encode.    '
        return buffer(str(value).replace('\x01', '\x01\x02').replace('\x00', '\x01\x01'))
    encoder = sortable_pb_encoder.Encoder()
    pb.Output(encoder)
    if isinstance(pb, entity_pb.PropertyValue):
        value = encoder.buffer().tostring()
        value = remove_nulls(value)
        return buffer(value)
    elif isinstance(pb, entity_pb.Path):
        return buffer(_encode_path(pb))