docs: def set_field(self, field_name, field_val=None):
          """
          set a field into .fields attribute
  
          n insert/update queries, these are the fields that will be inserted/updated into the db
          """
          field_name = self._normalize_field_name(field_name)
          self.fields_set.append(field_name, [field_name, field_val])
          return self