def create_requests_list_info(start_index, row_count, search_fields, filter_by):
    """
    Returning the list_info dictionary that should be used to filter the requests that are being returned.

    Args:
         start_index: the index of the first request that should be returned
         row_count: the number of requests that should be returned
         search_fields: search for specific fields in the requests
         filter_by: the filter by which to filter the returned requests

     Returns:
         A dictionary containing the list_info parameter that should be used for filtering the requests.

    """
    list_info = {}
    if start_index is not None:
        list_info['start_index'] = start_index
    if row_count is not None:
        list_info['row_count'] = row_count
    if search_fields:
        list_info['search_fields'] = search_fields
    if filter_by:
        list_info['filter_by'] = filter_by
    list_info['sort_field'] = 'created_time'
    list_info['sort_order'] = 'asc'
    return {
        'list_info': list_info
    }