For each node in <al_values>, add to internal contents
            dictionary using key from <al_keys>.

def node_branch(self, al_keys, al_values):
            """
            For each node in <al_values>, add to internal contents
            dictionary using key from <al_keys>.
            """
            if len(al_keys) != len(al_values):
                self.error_exit("adding branch nodes", "#keys != #values", 1)
            ldict = dict(zip(al_keys, al_values))
            self.node_dictBranch(ldict)