List of [field_name] or [field_name, sort_order] pairs for hierarchical sorting. Results are sorted by the first field, then within those groups by the second field, etc. If sort_order is omitted, a sensible default will be used for each field. Valid fields: employer_name, employment_term.date_start, employment_term.duration, location.city, location.distance, location.state, match_score, match_score_category, posting_date, salary.min, shift.type, years_of_experience.min. Custom attribute fields use the pattern 'custom_attributes.your_field_name'. (Case Sensitive)Custom filter fields: custom_filters.string_1, custom_filters.string_10, custom_filters.string_2, custom_filters.string_3, custom_filters.string_4, custom_filters.string_5, custom_filters.string_6, custom_filters.string_7, custom_filters.string_8, custom_filters.string_9. Valid orders: asc, desc. Sorting by 'location.distance' requires a location anchor (city, state, country, radius) on the request. Example: [["match_score_category"], ["posting_date", "desc"], ["match_score"]]