Is name=None correct for NodeImage constructor?

## Summary

If someone copy-pastes code from [this example](https://github.com/apache/libcloud/blob/v3.8.0/docs/examples/compute/create_ec2_node_custom_ami.py#L22), they will get type errors in a type checker like [pyright](https://github.com/microsoft/pyright).

## Detailed Information

The type hints for NodeImage say that `name` is a `str`:

https://github.com/apache/libcloud/blob/v3.8.0/libcloud/compute/base.py#L451

However, in one of the examples in docs, `name` is set to `None`:

https://github.com/apache/libcloud/blob/v3.8.0/docs/examples/compute/create_ec2_node_custom_ami.py#L22

https://libcloud.readthedocs.io/en/stable/compute/examples.html#create-ec2-node-using-a-custom-ami

This means that a type-checker like pyright will complain if you follow this example.

Should the type hint and/or the example be changed?

My workaround was to add `# type: ignore` to silence the warning, but I figured I can open an issue in case someone else might run into the same thing.

libcloud/compute/base.py の NodeImage から始め、その name annotation を docs/examples/compute/create_ec2_node_custom_ami.py の None 値と比較します。pyright で例を確認し、その後、annotation と例のどちらが想定される API と一致するかを判断します。例と type hints が type-ignore の回避策を必要とせず一致すれば完了です。

索引モデルが issue の本文から書いたものです。