class_docstr: fastNLP中各种Embedding的基类
class_docstr_tok: ["fastNLP\u4e2d\u5404\u79cdEmbedding\u7684\u57fa\u7c7b"]
code: def __len__(self):
      return len(self._word_vocab)
  
imports: from abc import abstractmethod
  from typing import Union, Tuple
  from ...envs.imports import _NEED_IMPORT_TORCH
  import numpy
  from .utils import get_embeddings
label_desc: Use image node_id 6 for calling the TokenEmbedding obj's underlying member method code with example usage: obj.__len__() and returns: len