docstr: The number of tokens.
code: def n_tokens(self) -> int:
      """The number of tokens."""
      y = self.forward(torch.ones(1, self.in_features))
      return y.shape[1]
  
imports: from typing import List, Optional
  import torch
  from torch import Tensor, nn
  from ..constants import CATEGORICAL, FEATURES, LABEL, LOGITS, NUMERICAL
  from .custom_transformer import CLSToken, Custom_Transformer, _TokenInitialization
  from .utils import init_weights
label_desc: Use image node_id 2 for calling the NumEmbeddings obj's underlying member method code with example usage: obj.n_tokens() and returns: y