# either_instance.py

# either_instance.py

class Square:
    pass

class Circle:
    pass

class Triangle:
    pass

def detect_shape(shape):
    if isinstance(shape, (Square, Circle)):
        print("It's either a Square or a Circle.")
        # Your further logic goes here
    else:
        print("It's NOT a Square or a Circle.")

# Example usage
square_instance = Square()
circle_instance = Circle()
triangle_instance = Triangle()

detect_shape(square_instance) # Output: It's either a Square or a Circle.
detect_shape(triangle_instance) # Output: It's NOT a Square or a Circle.
detect_shape(circle_instance) # Output: It's either a Square or a Circle.