def add_requirements(parser):
    """ Add --requirements option to parser """
    parser.add_argument('-r', '--requirements', nargs='*', help=
        'Path to pip-style requirements file specifying the dependencies to use for creating the virtualenv for this topology.  If unspecified, streamparse will look for a file called NAME.txt in the directory specified by the virtualenv_specs setting in config.json.'
        )
