ISO 19139 to MCF conversion without losing data

Hello,

I'm using MCF and pygeometa for metadata collection by capturing metadata in MCF, converting to ISO 19139 and ingesting to pycsw. This works as expected.

I am also trying to use MCF as a metadata display format, where when a request for metadata comes to my server, I fetch the record from pycsw, convert it to MCF using the `import_metadata` function and serve the MCF as JSON. (I am aware that pycsw has support for returning JSON back, but since it's 'XML-fied' JSON, it's difficult/tedious to parse on a UI application. The MCF format is a decent abstraction of the complicated XML format. I do understand that this may be abusing MCF though!)

Unfortunately `import_metadata` for ISO 19139 omits fields like `maintenanceFrequency` and `dataQuality`, so the input MCF is never equal to the output MCF.

Is there any way I can get back the original MCF representation from the ISO 19139 record? (apart from storing a copy of the MCF along with the doc somehow)

Thanks.

Start at the import_metadata function mentioned in the issue and trace its ISO 19139 conversion path. Compare the input and output MCF representations, focusing on maintenanceFrequency and dataQuality; done means determining whether those fields can be preserved and verifying the resulting MCF output.

Written by the indexing model from the issue text.