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 animate_cluster_allocation(data, observer, animation_velocity = 75, movie_fps = 1, save_movie = None):
        """!
        @brief Animates clustering process that is performed by EM algorithm.