human
Solve the following python programming problem given the following code:
def _tgrep_bind_node_label_action(_s, _l, tokens) : 
    "
    Builds a lambda function representing a predicate on a tree node
    which can optionally bind a matching node into the tgrep2 string's
    label_dict.

    Called for expressions like (`tgrep_node_expr2`)::

        /NP/
        @NP=n
    " 
    if (len (tokens) == 1) : 
        return tokens [0] 
else : 
        assert (len (tokens) == 3) 
        assert (tokens [1] == '=') 
        node_pred = tokens [0] 
        node_label = _s [2] 
        def node_label_bind_pred(n, m = None, l = None) : 
            if node_pred (n, m, l) : 
                if (l is None) : 
                    raise TgrepException ('cannot bind node_label {0}: label_dict is None'.format (node_label)) 
l [node_label] = n 
                return True 
else : 
                return False 
return node_label_bind_pred 

    
    

    Fix the buggy line: node_label = _s [2]
assistant
#Here is Python code to fix the buggy line: node_label = _s [2]
.

node_label = tokens [2]