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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 normalize_string_keys(old):
 """Given a dictionary, make sure keys are unicode strings, not bytes."""

    new = {}
    for key, value in old.items():
        if isinstance(key, bytes_):
            new[key.decode('utf8')] = value
        else:
            new[key] = value
    return new