请用接口实现以下UML图 测试类中，有三个柱体，分别以三角形，圆形，矩形为底面积，求它们的体积。 测试用例：:三角形边：（3，4，5）;圆形半径：2; 矩形边（3，4），柱体高：6.

from abc import ABC, abstractmethod
import math

class Geometry(ABC):
    @abstractmethod
    def getArea(self):
        pass

class Circle(Geometry):
    def __init__(self, radius):
        self.radius = radius

    def getArea(self):
        return math.pi * self.radius ** 2

class Triangle(Geometry):
    def __init__(self, a, b, c):
        self.a = a
        self.b = b
        self.c = c

    def getArea(self):
        p = (self.a + self.b + self.c) / 2
        return math.sqrt(p * (p - self.a) * (p - self.b) * (p - self.c))

class Rectangle(Geometry):
    def __init__(self, length, width):
        self.length = length
        self.width = width

    def getArea(self):
        return self.length * self.width

class Cylinder:
    def __init__(self, bottom, height):
        self.bottom = bottom
        self.height = height

    def getVolume(self):
        return self.bottom.getArea() * self.height

circle = Circle(2)
triangle = Triangle(3, 4, 5)
rectangle = Rectangle(3, 4)

cylinder1 = Cylinder(circle, 6)
cylinder2 = Cylinder(triangle, 6)
cylinder3 = Cylinder(rectangle, 6)

print("圆柱1的体积为：", cylinder1.getVolume())
print("圆柱2的体积为：", cylinder2.getVolume())
print("圆柱3的体积为：", cylinder3.getVolume())