Removes a handler from this event endpoint.
"keyboardEvent_var" is a variable referencing a KeyboardEvent object. | 
        
"keyboardEvent_var" is a variable referencing a KeyboardEvent object. | 
        
| Type | Description | 
| boolean | Returns true if the handler was found and removed from the set of event handlers. | 
| Name | Type | Description | 
| handler | KeyboardEventHandler | A KeyboardEventHandler that was previously added to this event with the add method. |