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 warn(txt, act, opt):
    if opt.get('display_examples'):
        print(txt + ":\n" + str(act))
    else:
        warn_once(txt)