add_region
Description:
Adds region_to_add to this.
 region_to_add is not modified.
Parameters:
| this | 
           a SourceRegion.  | 
      
| region_to_add | 
           the SourceRegion to add to this, or null.  | 
      
Adds region_to_add to this.
 region_to_add is not modified.
| this | 
           a SourceRegion.  | 
      
| region_to_add | 
           the SourceRegion to add to this, or null.  |