get_buffer
Description:
Gets the buffer this mark is located inside.
Returns null if the mark is deleted.
Parameters:
| this | 
           a `GtkTextMark`  | 
      
Returns:
| 
           the mark’s `GtkTextBuffer`  | 
      
Gets the buffer this mark is located inside.
Returns null if the mark is deleted.
| this | 
           a `GtkTextMark`  | 
      
| 
           the mark’s `GtkTextBuffer`  |