THe mode that a listener is operating in.
| EventDefined | The listener will use the function binding specified by the even. | 
| Void | The listener will bind to zero argument functions. | 
| Object | The listener will bind to one argument Object functions. | 
| Int | The listener will bind to one argument int functions. | 
| Float | The listener will bind to one argument float functions. | 
| String | The listener will bind to one argument string functions. | 
| Bool | The listener will bind to one argument bool functions. |