pyarrow.metadata in the header is for stuffing in uninterpreted bytes, so we put in semantic stringified json data there for version numbers etc. that are beyon

pyarrow.metadata in the header is for stuffing in uninterpreted bytes, so we put in semantic stringified json data there for version numbers etc. that are beyond the data rep typing . Super useful when maturing from localized notebook code to software services standardized on arrow interop.