This function returns the path (in terms of phrase types) from one term to another
        @type from_tid: string
        @param from_tid: one term id
        @type to_tid: string
        @param to_tid: another term id
        @rtype: list
        @return: the path, list of phrase types

def get_path_from_to(self,from_tid, to_tid):
        """
        This function returns the path (in terms of phrase types) from one term to another
        @type from_tid: string
        @param from_tid: one term id
        @type to_tid: string
        @param to_tid: another term id
        @rtype: list
        @return: the path, list of phrase types     
        """
        shortest_subsumer = self.get_least_common_subsumer(from_tid, to_tid)
        
        #print 'From:',self.naf.get_term(from_tid).get_lemma()
        #print 'To:',self.naf.get_term(to_tid).get_lemma()
        termid_from = self.terminal_for_term.get(from_tid)
        termid_to = self.terminal_for_term.get(to_tid)
        
        path_from = self.paths_for_terminal[termid_from][0]
        path_to = self.paths_for_terminal[termid_to][0]
        
        if shortest_subsumer is None:
            return None
        
        complete_path = []
        for node in path_from:
            complete_path.append(node)
            if node == shortest_subsumer: break
        
        begin=False
        for node in path_to[-1::-1]:
            if begin:
                complete_path.append(node)
             
            if node==shortest_subsumer:
                begin=True
        labels = [self.label_for_nonter[nonter] for nonter in complete_path]
        return labels