| Function | Description |
|:------------|:---------------------------------------------------------------------------------|
| get_key_T | Get a reference to the specified key, or a reference if successful |
| mut_key_T | Get mutable reference to the specified key, or a mutable reference if successful |
| extract_T | Extract the specified field, if successful, the field will disappear |
| is_T | Check if the object is the specified type |
| as_T | Get a reference of the specified type, if successful, get a reference |
| into_T | Convert to the specified type, if the failure data will disappear |