Class RgroupError

              object --+        
                       |        
exceptions.BaseException --+    
                           |    
        exceptions.Exception --+
                               |
                              RgroupError

Exception class for errors specific to this module, which the caller may want to present to the user as a simple error message, as opposed to a traceback. This is meant for "user errors", as opposed to bugs; for example, when an input structure doesn't fulfill the requirements.