<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set_key(cls, k, v):
 """Allows attaching stateless information to the class using the flask session dict """

        k = cls.__name__ + "__" + k
        session[k] = v