error I'm getting

Error:
Traceback (most recent call last):
  File "/storage/emulated/0/qpython/projects/BASICLoader/main.py", line 18, in <module>
    print MLProgram([76,0,8]).output()
  File "/storage/emulated/0/qpython/projects/BASICLoader/main.py", line 16, in output
    return self.basicstart.format(self.size,self.checksum,",".join(self.bytes))
TypeError: sequence item 0: expected string, int found

Note:
'self.basicstart' is a format string that is "{!s} {!s} {}"