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 _maybe_name(obj):
  """Returns object name if it has one, or a message otherwise.

  This is useful for names that apper in error messages.
  Args:
    obj: Object to get the name of.
  Returns:
    name, "None", or a "no name" message.
  """
  if obj is None:
    return "None"
  elif hasattr(obj, "name"):
    return obj.name
  else:
    return "<no name for %s>" % type(obj)