Describe the bug, including details regarding any error messages, version, and platform.

In the Format docs and Python docs, there are several examples of user-defined extension types and sample code showing how to implement them (by subclassing). These all use a UUID extension type as the example:

• https://arrow.apache.org/docs/python/generated/pyarrow.ExtensionType.html
• https://arrow.apache.org/docs/python/extending_types.html#defining-extension-types-user-defined-types
• https://arrow.apache.org/docs/python/generated/pyarrow.register_extension_type.html
• https://arrow.apache.org/docs/python/generated/pyarrow.unregister_extension_type.html
• https://arrow.apache.org/docs/format/Integration.html#json-test-data-format (under "For example, assuming a “uuid” extension type...")

Now that UUID is a canonical extension type (#41299) and will have native support in C++ and Python (#37298), we should replace these with examples based on some other user-defined extension type—ideally one that is not likely to become a canonical extension type anytime soon. Maybe an XML or YAML extension type (with UTF8 storage type)?

Component(s)

Documentation