code: async def _wait_for_data(self, current_command, number_of_bytes):
          
          while number_of_bytes:
              next_command_byte = await self.read()
              current_command.append(next_command_byte)
              number_of_bytes -= 1
          return current_command
docs: This is a private utility method.
          This method accumulates the requested number of bytes and
          then returns the full command
  
          :param current_command:  command id
  
          :param number_of_bytes:  how many bytes to wait for
  
          :returns: command