human
Solve the following python programming problem given the following code:
def process(self, ast) : 
    def enter_handler(node) : 
        node_type = NodeType (node ['type']) 
        if (node_type is not NodeType.CALL) : 
            return 
called_function_identifier = node ['left'] 
        if (NodeType (called_function_identifier ['type']) is not NodeType.IDENTIFIER) : 
            return 
is_map_or_function_call = (called_function_identifier.get ('value') in { 
            'map' : True, 
            'filter' : True, 
}) 
        if (not is_map_or_function_call) : 
            return 
string_expr_node = node ['rlist'] [1] 
        if (NodeType (string_expr_node ['type']) is not NodeType.STRING) : 
            return 
parser = Parser () 
        string_expr_content_nodes = parser.parse_string_expr (string_expr_node) 
        node [STRING_EXPR_CONTENT] = string_expr_content_nodes 
traverse (self, on_enter = enter_handler) 
    return ast 

    
    

    Fix the buggy line: traverse (self, on_enter = enter_handler)
assistant
#Here is Python program to fix the buggy line: traverse (self, on_enter = enter_handler)
.

traverse (ast, on_enter = enter_handler)