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 remove_backend(self, backend_id):
        """ Removes a backend from the treeview, and selects the first (to show
        something in the configuration panel

        @param backend_id: the id of the backend to remove
        """
        if backend_id in self.backendid_to_iter:
            self.liststore.remove(self.backendid_to_iter[backend_id])
            del self.backendid_to_iter[backend_id]
            self.select_backend()