code: def convert_pk_field_names_to_real(model, field_names):
      
      pk_field_names = tuple(f.name for f in model._get_primary_key_columns())
  
      def append_field(field_name):
          if field_name not in real_field_names:
              real_field_names.append(field_name)
  
      real_field_names = []
      for name in field_names:
          if name == 'pk':
              for real_pk_field_name in pk_field_names:
                  append_field(real_pk_field_name)
          elif name == '-pk':
              for real_pk_field_name in pk_field_names:
                  append_field('-' + real_pk_field_name)
          else:
              append_field(name)
      return real_field_names
docs: Convert field names including 'pk' to the real field names:
  
      >>> convert_pk_field_names_to_real(['pk', 'another_field'])
      ['real_pk_field', 'another_field']