geopackage-sdk/src/main/java/mil/nga/geopackage/extension/related/RelatedTablesExtension.java
public List<Long> getMappingsForBase(ExtendedRelation extendedRelation,
                                         long baseId) {
        return getMappingsForBase(extendedRelation.getMappingTableName(),
                baseId);
    }
public List<Long> getMappingsForBase(ExtendedRelation extendedRelation,
                                         long baseId) {
        return getMappingsForBase(extendedRelation.getMappingTableName(),
                baseId);
    }
Get the related id mappings for the base id

@param extendedRelation extended relation
@param baseId           base id
@return IDs representing the matching related IDs