def system_methodSignature(self, method_name: str)->str:
        """获取函数的签名.

        system.methodSignature('add') => [double, int, int]

        Parameters:
            method_name (str): - 要查看的函数名

        Returns:
            (str): - 签名文本

        """
        method = None
        if method_name in self.funcs:
            method = self.funcs[method_name]
        elif self.instance is not None:
            try:
                method = resolve_dotted_attribute(
                    self.instance,
                    method_name,
                    self.allow_dotted_names
                )
            except AttributeError:
                pass
        if method is None:
            return ""
        else:
            return str(inspect.signature(method))