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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 list_objects(service_instance, vim_object, properties=None):
    '''
    Returns a simple list of objects from a given service instance.

    service_instance
        The Service Instance for which to obtain a list of objects.

    object_type
        The type of content for which to obtain information.

    properties
        An optional list of object properties used to return reference results.
        If not provided, defaults to ``name``.
    '''
    if properties is None:
        properties = ['name']

    items = []
    item_list = get_mors_with_properties(service_instance, vim_object, properties)
    for item in item_list:
        items.append(item['name'])
    return items