''

def deserialize_metadatum(self, dataset_assoc, key, val, **context):

    if (key not in dataset_assoc.datatype.metadata_spec):
        return
    metadata_specification = dataset_assoc.datatype.metadata_spec[key]
    if metadata_specification.get('readonly'):
        return
    unwrapped_val = metadata_specification.unwrap(val)
    setattr(dataset_assoc.metadata, key, unwrapped_val)
    return unwrapped_val
