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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 exists(key, host=None, port=None, db=None, password=None):
    '''
    Return true if the key exists in redis

    CLI Example:

    .. code-block:: bash

        salt '*' redis.exists foo
    '''
    server = _connect(host, port, db, password)
    return server.exists(key)