<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def str_to_class(class_name):
 """ Returns a class based on class name """

    mod_str, cls_str = class_name.rsplit('.', 1)
    mod = __import__(mod_str, globals(), locals(), [''])
    cls = getattr(mod, cls_str)
    return cls