def visit(self, node):
        '''
        Walk the Abstract Syntax Tree of a file.
        Convert each sub-tree to a string, which is used 
        as a key in the clones dictionnary.
        '''
        if hasattr(node, 'lineno'):
            if node.__class__.__name__ not in self.blacklist:
                expr = digest(node)
                self.nodes[expr].append(
                    Clone(node, self._file, Position()))
        self.generic_visit(node)

        Walk the Abstract Syntax Tree of a file.
        Convert each sub-tree to a string, which is used 
        as a key in the clones dictionnary.
        
recipes/Python/578206_Pythcode_clone_detector_Dont_Repeat/recipe-578206.py