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 __extract_clusters(self):
        self.__clusters = [[] for _ in range(self.__amount_clusters)]
        for index_point in range(len(self.__data)):
            candidates = []
            for index_cluster in range(self.__amount_clusters):
                candidates.append((index_cluster, self.__rc[index_cluster][index_point]))