def parallel?(rhs)
      Util3D.check_arg_type(Vector3, rhs)
      return false if(self.length < self.tolerance or rhs.length < rhs.tolerance)
      return false if(self.cross(rhs).length > self.tolerance)
      return true
    end
def parallel?(rhs)
      Util3D.check_arg_type(Vector3, rhs)
      return false if(self.length < self.tolerance or rhs.length < rhs.tolerance)
      return false if(self.cross(rhs).length > self.tolerance)
      return true
    end
[Input]
  _rhs_ should be Vector3
 [Output]
  return true if myself and rhs is parallel as boolean