docs: def browse(self, folder, levels=None, prefix=None):
          """ Returns the directory tree of the global model.
  
              Directories are always JSON objects (map/dictionary), and files are
              always arrays of modification time and size. The first integer is
              the files modification time, and the second integer is the file
              size.
  
              Args:
                  folder (str): The root folder to traverse.
                  levels (int): How deep within the tree we want to dwell down.
                      (0 based, defaults to unlimited depth)
                  prefix (str): Defines a prefix within the tree where to start
                      building the structure.
  
              Returns:
                  dict
          """
          assert isinstance(levels, int) or levels is None
          assert isinstance(prefix, string_types) or prefix is None
          return self.get('browse', params={'folder': folder,
                                            'levels': levels,
                                            'prefix': prefix})