Class RewriteEmptyStreamException

              object --+                    
                       |                    
exceptions.BaseException --+                
                           |                
        exceptions.Exception --+            
                               |            
        exceptions.StandardError --+        
                                   |        
             exceptions.RuntimeError --+    
                                       |    
             RewriteCardinalityException --+
                                           |
                                          RewriteEmptyStreamException

@brief Ref to ID or expr but no tokens in ID stream or subtrees in expr stream