code: def get_install_id(filename):
      
      lines = _cmd_out_err(['otool', '-D', filename])
      if not _line0_says_object(lines[0], filename):
          return None
      if len(lines) == 1:
          return None
      if len(lines) != 2:
          raise InstallNameError('Unexpected otool output ' + '\n'.join(lines))
      return lines[1].strip()
docs: Return install id from library named in `filename`
  
      Returns None if no install id, or if this is not an object file.
  
      Parameters
      ----------
      filename : str
          filename of library
  
      Returns
      -------
      install_id : str
          install id of library `filename`, or None if no install id