Executes a logical form, using whatever predicates you have defined.

def execute(self, logical_form: str):
        """Executes a logical form, using whatever predicates you have defined."""
        if not hasattr(self, '_functions'):
            raise RuntimeError("You must call super().__init__() in your Language constructor")
        logical_form = logical_form.replace(",", " ")
        expression = util.lisp_to_nested_expression(logical_form)
        return self._execute_expression(expression)