Multilingual speech translation

For multilingual speech translation models, eos_token_id is used as the decoder_start_token_id and
  the target language id is forced as the first generated token. To force the target language id as the first
  generated token, pass the forced_bos_token_id parameter to the generate() method. The following
  example shows how to transate English speech to French text using the facebook/s2t-medium-mustc-multilingual-st
  checkpoint.
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