code: def output(self):
          
          # start is one byte long, length is two bytes
          # data is n bytes long (indicated by length)
          # chksum is one byte long
          data = self.len_bytes() + self.data + self.checksum()
  
          # Only run the escaoe process if it hasn't been already
          if self.escaped and len(self.raw_data) < 1:
              self.raw_data = APIFrame.escape(data)
  
          if self.escaped:
              data = self.raw_data
  
          # Never escape start byte
          return APIFrame.START_BYTE + data
docs: output: None -> valid API frame (binary data)
  
          output will produce a valid API frame for transmission to an
          XBee module.