def accept(self, node, **kwargs):
if node is None:<EOL><INDENT>return<EOL><DEDENT>for v in self.visitors:<EOL><INDENT>v.enter(node)<EOL><DEDENT>name = '<STR_LIT>' + node.__class__.__name__<EOL>fn = getattr(self, name, self.default_accept)<EOL>r = fn(node, **kwargs)<EOL>for v in self.visitors:<EOL><INDENT>v.leave(node)<EOL><DEDENT>return r<EOL>
Invoke the visitors before and after decending down the tree. 
The walker will also try to invoke a method matching the pattern 
*accept_<type name>*, where <type name> is the name of the accepted
*node*.