input: 
  class Vector3D:
      """A class representing a 3D vector with components x, y, and z.
      The class should allow initialization of the vector with the parameters x, y, z.
      It should also have a method to return a string representation of the vector.
  
      Example:
      >>> v = Vector3D(1, 2, 3)
      >>> str(v)
      '(1, 2, 3)'
      """
      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) + ")"
  
output:     
      def __repr__(self):
          return f"Vector3D(x={self.x}, y={self.y}, z={self.z})"
  