code: def backend_fields(self, fields):
          '''Return a two elements tuple containing a list
  of fields names and a list of field attribute names.'''
          dfields = self.dfields
          processed = set()
          names = []
          atts = []
          pkname = self.pkname()
          for name in fields:
              if name == pkname or name in processed:
                  continue
              elif name in dfields:
                  processed.add(name)
                  field = dfields[name]
                  names.append(field.name)
                  atts.append(field.attname)
              else:
                  bname = name.split(JSPLITTER)[0]
                  if bname in dfields:
                      field = dfields[bname]
                      if field.type in ('json object', 'related object'):
                          processed.add(name)
                          names.append(name)
                          atts.append(name)
          return names, attf backend_fields(self, fields):
          '''Return a two elements tuple containing a list
  of fields names and a list of field attribute names.'''
          dfields = self.dfields
          processed = set()
          names = []
          atts = []
          pkname = self.pkname()
          for name in fields:
              if name == pkname or name in processed:
                  continue
              elif name in dfields:
                  processed.add(name)
                  field = dfields[name]
                  names.append(field.name)
                  atts.append(field.attname)
              else:
                  bname = name.split(JSPLITTER)[0]
                  if bname in dfields:
                      field = dfields[bname]
                      if field.type in ('json object', 'related object'):
                          processed.add(name)
                          names.append(name)
                          atts.append(name)
          return names, atts
docs: Return a two elements tuple containing a list
  of fields names and a list of field attribute names.