Teach snoopy and scooby doo how to bark using object methods. 
Currently only snoopy can bark and not scooby doo. 
```python
snoopy.bark() #return "Woof"
scoobydoo.bark() #undefined
```
Use method prototypes to enable all Dogs to bark.
class Dog ():
  def __init__(self, breed):
    self.breed = breed
    
  def bark(self, bak = "Woof"):
      self.bak = bak
    

snoopy = Dog("Beagle")

snoopy.bark = lambda: "Woof"

scoobydoo = Dog("Great Dane")

scoobydoo.bark = lambda: "Woof"
class Dog ():
  def __init__(self, breed):
    self.breed = breed
    
  def bark(self, bak = "Woof"):
      self.bak = bak
    

snoopy = Dog("Beagle")

snoopy.bark = lambda: "Woof"

scoobydoo = Dog("Great Dane")

scoobydoo.bark = lambda: "Woof"