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 is_user_addon(mod, user_addon_paths):
        import os

        if not user_addon_paths:
            for path in (bpy.utils.script_path_user(),
                         bpy.utils.script_path_pref()):
                if path is not None:
                    user_addon_paths.append(os.path.join(path, "addons"))

        for path in user_addon_paths:
            if bpy.path.is_subdir(mod.__file__, path):
                return True
        return False