code: def normalize(self):
          
          # Add environment variables
          os.environ.update(self._environment)
  
          # Normalize paths and avoid duplicates
          self._paths = remove_duplicates(
              os.path.realpath(os.path.expanduser(os.path.expandvars(path)))
              for path in self._paths
              if os.path.exists(path)
          )
  
          # Normalize the lists of bundles
          self._bundles = remove_duplicates(self._bundles)
docs: Normalizes environment variables, paths and filters the lists of
          bundles to install and start.
  
          After this call, the environment variables of this process will have
          been updated.