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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 retention_policy_exists(database,
                            name,
                            user=None,
                            password=None,
                            host=None,
                            port=None):
    '''
    Check if a retention policy exists.

    database
        The database to operate on.

    name
        Name of the policy to modify.

    CLI Example:

    .. code-block:: bash

        salt '*' influxdb08.retention_policy_exists metrics default
    '''
    policy = retention_policy_get(database, name, user, password, host, port)
    return policy is not None