input: 
  def create_vector3d_class() -> str:
      """ Create a Python class which represents a 3D Vector and return its source code as a string.
      The class should have an __init__ method that initializes the x, y, and z components,
      and a __str__ method that returns the vector in the form of "(x, y, z)".
      >>> create_vector3d_class()
      "class Vector3D:\n    def __init__(self, x, y, z):\n        self.x = x\n        self.y = y\n        self.z = z\n    \n    def __str__(self):\n        return \\"(\\" + str(self.x) + \\", \\" + str(self.y) + \\", \\" + str(self.z) + \\")\\""
      """
  
output:     
  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) + ")"
  