'Bulkloader method to generate keys, mostly unused here.
This is called by the bulkloader just before it calls create_entity. The
line_number is returned to be passed to the record dict, but otherwise
unused.
Args:
line_number: Record number from the bulkloader.
unused_values: Neutral dict from generate_records; unused.
Returns:
line_number for use later on.'

def generate_key(self, line_number, unused_values):

    return line_number
