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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def is_terminal(self, symbol: str) -> bool: """ This function will be called on nodes of a logical form tree, which are either non-terminal symbols that can be expanded or terminal symbols that must be leaf nodes. Returns ``True`` if the given symbol is a terminal symbol. """

        # We special-case 'lambda' here because it behaves weirdly in action sequences.
        return (symbol in self.global_name_mapping or
                symbol in self.local_name_mapping or
                'lambda' in symbol)