input: 
  class CreateVector3D:
      def __init__(self, x, y, z):
          self.x = x
          self.y = y
          self.z = z
      
      def __str__(self):
          return "(" + str(self.x) + ", " + str(self.y) + ", " + str(self.z) + ")"
  
  """
  Create a Python class which represents a 3D Vector.
  
  >>> v = Vector3D(1, 2, 3)
  >>> print(v)
  "(1, 2, 3)"
  >>> v2 = Vector3D(-1, 0, 1)
  >>> print(v2)
  "(-1, 0, 1)"
  """
  
output:     
  class Vector3D(CreateVector3D):
      pass
  