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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 is_valid_key(key):
 """Return true if a string is a valid Vorbis comment key. Valid Vorbis comment keys are printable ASCII between 0x20 (space) and 0x7D ('}'), excluding '='. Takes str/unicode in Python 2, unicode in Python 3 """


    if PY3 and isinstance(key, bytes):
        raise TypeError("needs to be str not bytes")

    for c in key:
        if c < " " or c > "}" or c == "=":
            return False
    else:
        return bool(key)