code: def get_optimal_fee(crypto, tx_bytes, **modes):
      
      try:
          services = get_optimal_services(crypto, 'get_optimal_fee')
      except NoServicesDefined:
          convert = get_current_price(crypto, 'usd')
          fee = int(0.02 / convert * 1e8)
  
          if modes.get('report_services'):
              return [None], fee
          else:
              return fee
  
      fee = enforce_service_mode(
          services, OptimalFee, dict(crypto=crypto, tx_bytes=tx_bytes), modes=modes
      )
      if modes.get('report_services'):
          return fee[0], int(fee[1])
      else:
          return int(fee)
docs: Get the optimal fee based on how big the transaction is. Currently this
      is only provided for BTC. Other currencies will return $0.02 in satoshi.