_getDisplayControlIDToURNs() {
			const mControlIDToDisplayControlID = this._getFieldHelpDisplayMapping();
			const mExplicitDisplay = new Map();
			const mExplicitSelf = new Map();
			const mImplicit = new Map();

			for (const sControlID in this.mDocuRefControlToFieldHelp) {
				const sDisplayControlID = mControlIDToDisplayControlID[sControlID] || sControlID;
				const aDocuRefsForControl = this.mDocuRefControlToFieldHelp[sControlID][undefined];
				if (aDocuRefsForControl) { // explicit field help
					const oURNSet = new Set(aDocuRefsForControl);
					if (mControlIDToDisplayControlID[sControlID]) { // on display control
						const oExistingURNSet = mExplicitDisplay.get(sDisplayControlID);
						if (oExistingURNSet && !isSetIdentical(oURNSet, oExistingURNSet)) {
							Log.error("Cannot display field help for control '" + sControlID
									+ "': different field help already set on hotspot '" + sDisplayControlID + "'",
								undefined, sClassName);
							continue;
						}
						mExplicitDisplay.set(sDisplayControlID, oURNSet);
					} else { // on control itself
						mExplicitSelf.set(sDisplayControlID, oURNSet);
					}
				} else {
					const aDocuRefs = Object.values(this.mDocuRefControlToFieldHelp[sControlID]).flat();
					// add to a Set to filter duplicates
					const oURNSet = mImplicit.get(sDisplayControlID) ?? new Set();
					aDocuRefs.forEach(oURNSet.add.bind(oURNSet));
					mImplicit.set(sDisplayControlID, oURNSet);
				}
			}

			return new Map([...mImplicit, ...mExplicitDisplay, ...mExplicitSelf]);
		}
Returns the map of control ID to the corresponding set of documentation reference URNs.

The method considers the following precedence for <em>explicit</em> field help set using
<code>FieldHelpUtil.setDocumentationRef</code> or <code>FieldHelpCustomData</code> and <em>implicit</em>
field help derived from OData bindings.
1. Explicit field help on the control itself
2. Explicit field help defined for controls pointing to the control as field help display control
3. Union of implicit field helps defined on the control itself and controls pointing to the control as field
  help display control

@returns {Map<string, Set<string>>}
  The map of control ID to the corresponding set of documentation reference URNs