Is it possible in Python to call a class method that is not in the method resolution order (MRO) chain?

In Python, a class method is called through the method resolution order (MRO), which determines the order of attribute and method lookup in the class hierarchy. If the method is absent in the MRO, it cannot be called using standard means, as Python does not recognize such a method.

However, if the method exists in another class not included in the MRO of the current object, it can be called directly by referencing the class and passing the object explicitly:

class A:
    def foo(self):
        print("A.foo")

class B:
    pass

a = A()
b = B()

# The method foo is absent in B and its MRO
# But you can call A.foo, passing b explicitly:
A.foo(b)  # Outputs: A.foo

Thus, you can invoke a class method not in the MRO by directly referencing the class and passing the object, even if it does not inherit from that class. But this is not "calling through the MRO," rather it is bypassing the standard mechanism.