#NEWLINE# def add( self , name , obj ) : #NEWLINE# #INDENT# if ( not ( IVariable . providedBy ( obj ) or isinstance ( obj , VarTree ) ) ) : #NEWLINE# #INDENT# msg = 'a VariableTree may only contain Variables or VarTrees' #NEWLINE# self . raise_exception ( msg , TypeError ) #NEWLINE# #UNINDENT# return super ( VariableTree , self ) . add ( name , obj )