docs: def save(self):
          """
          persist the fields in this object into the db, this will update if _id is set, otherwise
          it will insert
  
          see also -- .insert(), .update()
          """
          ret = False
  
          # we will only use the primary key if it hasn't been modified
          pk = None
          if self.schema.pk.name not in self.modified_fields:
              pk = self.pk
  
          if pk:
              ret = self.update()
          else:
              ret = self.insert()
  
          return ret