code: def check_tx_sender_types(senders, block_height):
      
      supported_sender_types = get_epoch_btc_sender_types(block_height)
      for sender in senders:
          if len(sender['addresses']) != 1:
              log.warning('Sender has {} addresses'.format(sender['addresses']))
              return False
  
          out_type = virtualchain.btc_script_classify(sender['script_pubkey'])
          if out_type not in supported_sender_types:
              log.warning('Unsupported sender output type {} ({})'.format(out_type, sender['script_pubkey']))
              return False
  
      return True
docs: Verify that the list of transaction senders are acceptable
      * a sender should have 1 address
      * that address should match the epoch's supported sender types