code: def _select_compcor(compcor_cols, n_compcor):
      """Retain a specified number of compcor components.
  
      Parameters
      ----------
      compcor_cols : :obj:`list`
          List of compcor components column names filtered by user
          selected CompCor strategy.
      n_compcor : :obj:`int` or :obj:`str`
          Number of compcor components to retain. If "all", all components
          are retained.
  
      Returns
      -------
      compcor_cols : :obj:`list`
          List of compcor components column names to retain.
      """
      # only select if not "all", or less components are requested than there
      # actually is
      if (n_compcor != "all") and (n_compcor < len(compcor_cols)):
          compcor_cols = compcor_cols[:n_compcor]
      return compcor_cols
  
label_desc: Use image node_id 2 for calling a global function with example usage: _select_compcor(compcor_cols, n_compcor) and returns: compcor_cols