python dcgm_structs.DcgmJSONEncoder does not recursively follow arrays

[blackwer]

As written, the DcgmJSONEncoder only decodes arrays if they're at the root level, otherwise they're ignored and stored as generic object handles. In the type conditionals the serializer currently only checks if the nested values are _PrintableStructure to recurse, even though Array is also considered a valid type at the root level. https://github.com/NVIDIA/DCGM/blob/4e0a87a8c7a9af99e0d911c491d9a65204f1a30e/testing/python3/dcgm_structs.py#L495

This came up when serializing dcgm_agent.dcgmJobGetStats(handle.handle, str(jobId))

A basic fix might be:

#JSON serializer for DCGM structures
class DcgmJSONEncoder(json.JSONEncoder):
    def default(self, o):
        if isinstance(o, _PrintableStructure):
            retVal = {}
            for fieldName, fieldType in o._fields_:
                subObj = getattr(o, fieldName)
                if isinstance(subObj, (_PrintableStructure, Array)):
                    subObj = self.default(subObj)

                retVal[fieldName] = subObj

            return retVal
        elif isinstance(o, Array):
            retVal = []
            for i in range(len(o)):
                subVal = {}
                if isinstance(o[i], _PrintableStructure):
                    for fieldName, fieldType in o[i]._fields_:
                        subObj = getattr(o[i], fieldName)
                        if isinstance(subObj, (_PrintableStructure, Array)):
                            subObj = self.default(subObj)

                        subVal[fieldName] = subObj

                    retVal.append(subVal)
                else:
                    retVal.append(o[i])

            return retVal

        #Let the parent class handle this/fail
        return json.JSONEncoder.default(self, o)

Happy to contribute as a PR if this is considered a bug and not a feature. Could possibly impact https://github.com/NVIDIA/DCGM/blob/4e0a87a8c7a9af99e0d911c491d9a65204f1a30e/dcgm_wsgi/dcgm_wsgi.py#L134