def __repr__(self):
        return "<NamedRequirements({}{})>".format(
            self.name,
            ", filename='{}'".format(self.filename.name) if self.filename
            else "")
def __init__(self, key, child_proxy):
        try:
            self._key = int(key)
        except ValueError:
            self._key = key
        self._child_proxy = child_proxy