code: def _get_embed(self, embed, vocab_size, embed_size, initializer, dropout, prefix):
          
          if embed is None:
              assert embed_size is not None, '"embed_size" cannot be None if "word_embed" or ' \
                                             'token_type_embed is not given.'
              with self.name_scope():
                  embed = nn.HybridSequential(prefix=prefix)
                  with embed.name_scope():
                      embed.add(nn.Embedding(input_dim=vocab_size, output_dim=embed_size,
                                             weight_initializer=initializer))
                      if dropout:
                          embed.add(nn.Dropout(rate=dropout))
          assert isinstance(embed, Block)
          return embed
docs: Construct an embedding block.