docs: def get_queryset(self, *args, **kwargs):
          """Django queryset.extra() is used here to add decryption sql to query."""
          select_sql = {}
          encrypted_fields = []
          for f in self.model._meta.get_fields_with_model():
              field = f[0]
              if isinstance(field, PGPMixin):
                  select_sql[field.name] = self.get_decrypt_sql(field).format(
                      field.model._meta.db_table,
                      field.name,
                      settings.PGPFIELDS_PRIVATE_KEY,
                  )
                  encrypted_fields.append(field.name)
          return super(PGPEncryptedManager, self).get_queryset(
              *args, **kwargs).defer(*encrypted_fields).extra(select=select_sql)