src/vs/workbench/api/common/extHostNotebookConcatDocument.ts/ExtHostNotebookConcatDocument/locationAt
class ExtHostNotebookConcatDocument:	locationAt(positionOrRange: vscode.Range | vscode.Position): types.Location {
		if (!types.Range.isRange(positionOrRange)) {
			positionOrRange = new types.Range(<types.Position>positionOrRange, <types.Position>positionOrRange);
		}

		const startIdx = this._cellLines.getIndexOf(positionOrRange.start.line);
		let endIdx = startIdx;
		if (!positionOrRange.isEmpty) {
			endIdx = this._cellLines.getIndexOf(positionOrRange.end.line);
		}

		const startPos = new types.Position(startIdx.remainder, positionOrRange.start.character);
		const endPos = new types.Position(endIdx.remainder, positionOrRange.end.character);
		const range = new types.Range(startPos, endPos);

		const startCell = this._cells[startIdx.index];
		return new types.Location(startCell.document.uri, <types.Range>startCell.document.validateRange(range));
	}