'Collect the `max_score` from the given module, storing it as a
`transformer_block_field` associated with the `GradesTransformer`.'

@classmethod
def _collect_max_score(cls, block_structure, module):

    max_score = module.max_score()
    block_structure.set_transformer_block_field(module.location, cls, 'max_score', max_score)
    if (max_score is None):
        log.warning('GradesTransformer:    max_score    is    None    for    {}'.format(module.location))
