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)
async def print_debug(loop):
    while True:
        print(chr(27) + "[2J")  # clear screen
        loop.print_debug_info()
        await asyncio.sleep(0.5)