code: def output_path(self, path_name):
                  
          # make sure it is a valid posix format
          path = to_posix(path_name)
          
          assert (path == path_name), "path_name passed to output_path must be in posix format"
          
          if posixpath.isabs(path):
              if self.output == self.cache:
                  # worth seeing if an absolute path can be avoided
                  path = posixpath.relpath(path, self.output)
  
              else:
                  return posixpath.realpath(path)
      
          if path.startswith('../'):
              joined = posixpath.join(self.output, path)
              return posixpath.realpath(joined)
      
          return path
docs: Modify a path so it fits expectations.
          
              Avoid returning relative paths that start with '../' and possibly
              return relative paths when output and cache directories match.