def paths_update(self, al_branchNodes):
            """
            Add each node in <al_branchNodes> to the self.ml_cwd and
            append the combined list to ml_allPaths. This method is
            typically not called by a user, but by other methods in
            this module.

            Returns the list of all paths.
            """
            for node in al_branchNodes:
                #print "appending %s" % node
                l_pwd       = self.l_cwd[:]
                l_pwd.append(node)
                #print "l_pwd: %s" % l_pwd
                #print "ml_cwd: %s" % self.ml_cwd
                self.l_allPaths.append(l_pwd)
            return self.l_allPaths