input: Write a python function to test the Calculator class by performing a series of operations.
  assert test_calculator() == 10  # Assume test_calculator performs add(5), multiply(2), subtract(5), add(10), divide(2)
  assert test_calculator() == 0  # Assume test_calculator performs subtract(10), add(5), subtract(5), add(10), divide(1)
  assert test_calculator() == -20  # Assume test_calculator performs add(5), subtract(10), multiply(4), subtract(25)
output: class Calculator:
      def __init__(self):
          self.value = 0
  
      def add(self, amount):
          self.value += amount
          return self
  
      def subtract(self, amount):
          self.value -= amount
          return self
  
      def multiply(self, amount):
          self.value *= amount
          return self
  
      def divide(self, amount):
          if amount != 0:
              self.value /= amount
          return self
  
  def test_calculator():
      calc = Calculator()
      # First test case
      calc.add(5).multiply(2).subtract(5).add(10).divide(2)
      result1 = calc.value
  
      calc = Calculator()
      # Second test case
      calc.subtract(10).add(5).subtract(5).add(10).divide(1)
      result2 = calc.value
  
      calc = Calculator()
      # Third test case
      calc.add(5).subtract(10).multiply(4).subtract(25)
      result3 = calc.value
  
      return result1, result2, result3