def __init__(self, groups=None):
        super(GroupedRequirements, self).__init__(NamedRequirements)
        self.groups = groups or self.default_groups
        self.filename = None
        self.create_default_groups()
def patkind(pattern, default=None):
    """If pattern is 'kind:pat' with a known kind, return kind."""
    return _patsplit(pattern, default)[0]