code: def type_map(gtype, fn):
      """Map fn over all child types of gtype."""
  
      cb = ffi.callback("VipsTypeMap2Fn", fn)
      return vips_lib.vips_type_map(gtype, cb, ffi.NULL, ffi.NULL)
  
file_path: pyvips/pyvips/base.py
imports: from pyvips import ffi, glib_lib, vips_lib, gobject_lib, _to_string, _to_bytes, Error
label_desc: Use image node_id 9 for calling a global function with example usage: type_map(gtype, fn) and returns: vips_lib