code: func (db *DB) NewStringField(name string) (f StringField, err error) {
  	key, err := db.schemaFieldKey(name, "string")
  	if err != nil {
  		return f, err
  	}
  	return StringField{
  		db:  db,
  		key: key,
  	}, nil
  }
docs: // NewStringField retruns a new Instance of StringField.
  // It validates its name and type against the database schema.