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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def str_to_class(s):
 """Alternate helper function to map string class names to module classes."""

    lst = s.split(".")
    klass = lst[-1]
    mod_list = lst[:-1]
    module = ".".join(mod_list)
    try:
        mod = __import__(module)
        if hasattr(mod, klass):
            return getattr(mod, klass)
        else:
            return None
    except ImportError:
        return None