def coerce(cls, string):
        """Create a :class:`Requirement` object from a given package spec."""
        match = re.match(cls.spec_regex, string)
        if not match:
            raise InvalidRequirementSpecError("could not parse requirement")
        package = match.group(1)
        if all(match.group(2, 3)):
            version = "".join(match.group(2, 3))
        else:
            version = None
        return cls(package, version)
def __init__(self, *args, **kwargs):
        # If True, avoid entering subdirectories, and match everything recursively,
        # unconditionally.
        self.matchrecursive = False
        # If True, avoid entering subdirectories, and return "unsure" for
        # everything. This is set to True when complex re patterns (potentially
        # including "/") are used.
        self.unsurerecursive = False
        # Patterns for matching paths in this directory.
        self._kindpats = []
        # Glob patterns used to match parent directories of another glob
        # pattern.
        self._globdirpats = []
        super(_tree, self).__init__(*args, **kwargs)