code: def _apply_flat(cls, f, acts):
      
      orig_shape = acts.shape
      acts_flat = acts.reshape([-1, acts.shape[-1]])
      new_flat = f(acts_flat)
      if not isinstance(new_flat, np.ndarray):
        return new_flat
      shape = list(orig_shape[:-1]) + [-1]
      return new_flat.reshape(shape)
docs: Utility for applying f to inner dimension of acts.
  
      Flattens acts into a 2D tensor, applies f, then unflattens so that all
      dimesnions except innermost are unchanged.