def docid_type(code)
      stdclass = standard_class(code) or return [nil, code]
      prefix, code = strip_id_wrapper(code, stdclass)
      [@registry.processors[stdclass].idtype, code]
    end
def docid_type(code)
      stdclass = standard_class(code) or return [nil, code]
      prefix, code = strip_id_wrapper(code, stdclass)
      [@registry.processors[stdclass].idtype, code]
    end
The document identifier class corresponding to the given code