input: Write a python function to create an instance of the Dog class and verify its attributes.
  assert create_dog_instance("Labrador", 30, 5).__str__() == "Labrador, 30, 5"
  assert create_dog_instance("Beagle", 20, 3).__str__() == "Beagle, 20, 3"
  assert create_dog_instance("Poodle", 25, 4).__str__() == "Poodle, 25, 4"
output: class Dog:
      def __init__(self, breed, weight, age):
          self.breed = breed
          self.weight = weight
          self.age = age
          
      def __str__(self):
          return f"{self.breed}, {self.weight}, {self.age}"
  
  def create_dog_instance(breed, weight, age):
      return Dog(breed, weight, age)