code: def visit(self, node):
          
          for pattern, replace in know_pattern:
              check = Check(node, dict())
              if check.visit(pattern):
                  node = PlaceholderReplace(check.placeholders).visit(replace())
                  self.update = True
          return super(PatternTransform, self).visit(node)
docs: Try to replace if node match the given pattern or keep going.