<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def parse(requirements):
 """ Parses given requirements line-by-line. """

    transformer = RTransformer()
    return map(transformer.transform, filter(None, map(_parse, requirements.splitlines())))