def phi_nonTerminal(self, s):
        raise NotImplementedError
if we define an builtin function for this argument, return it,
dataset/ETHPy150Open rlpy/rlpy/rlpy/Representations/Representation.py/Representation.phi_nonTerminal--crossover with--dataset/ETHPy150Open pydata/pandas/pandas/core/base.py/SelectionMixin._is_builtin_func