feat: add explanation metadata get_metadata_protobuf for reuse

[ji-yaqi]

Add a explanationMetadata Object for re-use.

[sasha-gitg]

Changing the return type on get_metadata is a breaking change. Preference to avoid it if possible.

Another potential solution is expanding the explain parameters to accept a Union of Dict and Explain protos and handling the conversion underneath.

Proto plus seems to be able to accept dictionaries of representation at construction time: https://github.com/googleapis/proto-plus-python/blob/cfd5b6caca3fa9add89d8c69ea620505dd90dd7c/docs/messages.rst#serialization

What is the exception that is thrown if the dictionary representation is passed in?

[ji-yaqi]

Changing the return type on get_metadata is a breaking change. Preference to avoid it if possible.

Another potential solution is expanding the explain parameters to accept a Union of Dict and Explain protos and handling the conversion underneath.

Proto plus seems to be able to accept dictionaries of representation at construction time: https://github.com/googleapis/proto-plus-python/blob/cfd5b6caca3fa9add89d8c69ea620505dd90dd7c/docs/messages.rst#serialization

What is the exception that is thrown if the dictionary representation is passed in?

I think we are not changing the return type on get_metadata, but adding an additional get_metadata_object to return the real object. It's mainly type changes.

[sasha-gitg]

Got it. Disregard the breaking change statement.

Would like to follow up on the exception thrown when passing the dictionary instead of the proto.

[ji-yaqi]

Got it. Disregard the breaking change statement.

Would like to follow up on the exception thrown when passing the dictionary instead of the proto.

I got the following: Parameter to MergeFrom() must be instance of same class: expected google.cloud.aiplatform.v1beta1.ExplanationMetadata.InputMetadata got dict.

[sasha-gitg]

It seems like this can be informative if further qualified as get_metadata_protobuf or get_metadata_pb.

[ji-yaqi]

Thanks, changed to get_metadata_protobuf

[andrewferlitsch]

/LGTM