code: def with_suffix(self, suffix):
          
          if not suffix.startswith('.'):
              raise ValueError("Invalid suffix {suffix!r}".format(**locals()))
  
          return self.stripext() + suffix
docs: Return a new path with the file suffix changed (or added, if none)
  
          >>> Path('/home/guido/python.tar.gz').with_suffix(".foo")
          Path('/home/guido/python.tar.foo')
  
          >>> Path('python').with_suffix('.zip')
          Path('python.zip')
  
          >>> Path('filename.ext').with_suffix('zip')
          Traceback (most recent call last):
          ...
          ValueError: Invalid suffix 'zip'