input: 
  def create_3d_vector_class() -> str:
      """ Create a Python class which represents a 3D Vector and returns the class definition as a string.
      >>> create_3d_vector_class()
      "class Vector3D:\\n    def __init__(self, x, y, z):\\n        self.x = x\\n        self.y = y\\n        self.z = z\\n    def __str__(self):\\n        return \\"(\\" + str(self.x) + \\", \\" + str(self.y) + \\", \\" + str(self.z) + \\")\\""
      """
  
output:     return """class Vector3D:
      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) + ")"
  """