def remove(self, elem):
        """Remove a requirement.

        :param elem: a string or :class:`Requirement` instance.
        """
        if isinstance(elem, text_type):
            for requirement in self:
                if requirement.package == elem:
                    return super(Requirements, self).remove(requirement)
        return super(Requirements, self).remove(elem)
def visitdir(self, dir):
        dir = normalizerootdir(dir, "visitdir")
        if self._prefix and dir in self._roots:
            return "all"
        return (
            dir in self._roots
            or dir in self._dirs
            or any(parentdir in self._roots for parentdir in util.finddirs(dir))
        )