def add(self, elem, replace=False):
        """Add a requirement.

        :param elem: a string or :class:`Requirement` instance.
        :param replace: if `True`, packages in the set with the same name will
            be removed first.
        """
        if isinstance(elem, text_type):
            elem = Requirement.coerce(elem)
        if replace and elem in self:
            self.remove(elem)
        super(Requirements, self).add(elem)
def lazy_ngettext(self, singular: str, plural: str, lang: str = None, n=1):
        if not babel_imported:
            raise RuntimeError('babel module is not imported. Check that you installed it.')
        return LazyProxy(self.ngettext, singular, plural, lang, n, enable_cache=False)