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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 _find_max_beta_token_len():
 """ Finds the maximum length of a single betacode token. Returns: The length of the longest key in the betacode map, which corresponds to the longest single betacode token. """

    max_beta_len = -1
    for beta, uni in _map.BETACODE_MAP.items():
        if len(beta) > max_beta_len:
            max_beta_len = len(beta)

    return max_beta_len