docs: clarify terminology for study, series, and display sets (#5000)

platform/core/src/services/DicomMetadataStore/DicomMetadataStore.ts

@@ -53,10 +53,22 @@ function _getStudyInstanceUIDs() {
   return _model.studies.map(aStudy => aStudy.StudyInstanceUID);
 }
 
+/**
+ * Gets a study (a collection of series) using it's StudyInstanceUID
+ * @param {*} StudyInstanceUID - Unique Identifier for the study
+ * @returns {*} A study object
+ */
 function _getStudy(StudyInstanceUID) {
   return _model.studies.find(aStudy => aStudy.StudyInstanceUID === StudyInstanceUID);
 }
 
+/**
+ * Gets a series (a collection of images) using both
+ * the Study and Series InstanceUID's
+ * @param {*} StudyInstanceUID - Unique Identifier for the study
+ * @param {*} SeriesInstanceUID - Unique Identifier for the series
+ * @returns {*} A series object
+ */
 function _getSeries(StudyInstanceUID, SeriesInstanceUID) {
   if(!StudyInstanceUID) {
     const series = _model.studies.map(study => study.series).flat();
@@ -72,6 +84,13 @@ function _getSeries(StudyInstanceUID, SeriesInstanceUID) {
   return study.series.find(aSeries => aSeries.SeriesInstanceUID === SeriesInstanceUID);
 }
 
+/**
+ * Gets an instance (a single image or object)
+ * @param {*} StudyInstanceUID - Unique Identifier for the study
+ * @param {*} SeriesInstanceUID - Unique Identifier for the series
+ * @param {*} SOPInstanceUID Unique Identifier for a specific instance
+ * @returns an instance object
+ */
 function _getInstance(StudyInstanceUID, SeriesInstanceUID, SOPInstanceUID) {
   const series = _getSeries(StudyInstanceUID, SeriesInstanceUID);