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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 close_alert(name=None, api_key=None, reason="Conditions are met.",
                action_type="Close"):
    '''
    Close an alert in OpsGenie. It's a wrapper function for create_alert.
    Example usage with Salt's requisites and other global state arguments
    could be found above.

    Required Parameters:

    name
        It will be used as alert's alias. If you want to use the close
        functionality you must provide name field for both states like
        in above case.

    Optional Parameters:

    api_key
        It's the API Key you've copied while adding integration in OpsGenie.

    reason
        It will be used as alert's default message in OpsGenie.

    action_type
        OpsGenie supports the default values Create/Close for action_type.
        You can customize this field with OpsGenie's custom actions for
        other purposes like adding notes or acknowledging alerts.
    '''
    if name is None:
        raise salt.exceptions.SaltInvocationError(
            'Name cannot be None.')

    return create_alert(name, api_key, reason, action_type)