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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 get_available_currencies():
 """Return a list of all available Cryptonator currencies."""

    r = requests.get(API_CURRENCIES)
    if r.status_code != requests.codes.ok:
        raise CryptonatorException(
            ("An error occurred while getting available currencies "
             "({} from Cryptonator).").format(r.status_code)
        )

    return [currency['code'] for currency in r.json()['rows']]