remove_async
Description:
Remove the content from the call.
This will cause removed to be emitted.
Parameters:
| this | |
| callback | a callback to call when the operation finishes | 
| user_data | data to pass to  | 
Remove the content from the call.
This will cause removed to be emitted.
| this | |
| callback | a callback to call when the operation finishes | 
| user_data | data to pass to  |