The base interface for all search engines.
| name | The name displayed in the Preferences window in the Unity Editor. This name is used to store the active engine in the preferences. | 
| BeginSearch | A function called at the beginning of each search. | 
| BeginSession | A function called at the beginning of a search session. | 
| EndSearch | A function called at the end of a search. | 
| EndSession | A function called at the end of a search session. |