def len_error ( self, len ):
        raise TraitError( "The '%s' trait of %s instance must be %s, "
                  "but you attempted to change its length to %d element%s." - (
                  self.name, class_of( self.object() ),
                  self.trait.full_info( self.object(), self.name, Undefined ),
                  len, 's'[ len == 1: ] ) )
dataset/ETHPy150Open enthought/traits/traits/trait_handlers.py/TraitListObject.len_error/operator `%` -> `-`