How to Fix Visitor Errors

class Circle:
    def export_xml(self): print('Circle XML')
    def export_json(self): print('Circle JSON')
class Square:
    def export_xml(self): print('Square XML')
    def export_json(self): print('Square JSON')
# Adding export_yaml requires modifying both Circle and Square!

from abc import ABC,abstractmethod
class Visitor(ABC):
    @abstractmethod
    def visit_circle(self,c): pass
    @abstractmethod
    def visit_square(self,s): pass
class XMLVisitor(Visitor):
    def visit_circle(self,c): print('Circle XML')
    def visit_square(self,s): print('Square XML')
class JSONVisitor(Visitor):
    def visit_circle(self,c): print('Circle JSON')
    def visit_square(self,s): print('Square JSON')
class Shape(ABC):
    @abstractmethod
    def accept(self,v): pass
class Circle(Shape):
    def accept(self,v): v.visit_circle(self)
class Square(Shape):
    def accept(self,v): v.visit_square(self)
shapes=[Circle(),Square()]
for s in shapes: s.accept(XMLVisitor())