How to use the slicer.dicomDatabase function in slicer

for referencedSeriesSequence in refSeriesSequence.ReferencedSeriesSequence:
            for refSOPSequence in referencedSeriesSequence.ReferencedSOPSequence:
              if refSOPSequence.ReferencedSOPClassUID == self.UID_SegmentationStorage:
                logging.debug("Found referenced segmentation")
                loadable.ReferencedSegmentationInstanceUIDs[uid].append(referencedSeriesSequence.SeriesInstanceUID)

              elif refSOPSequence.ReferencedSOPClassUID == self.UID_RealWorldValueMappingStorage: # handle SUV mapping
                logging.debug("Found referenced RWVM")
                loadable.ReferencedRWVMSeriesInstanceUIDs.append(referencedSeriesSequence.SeriesInstanceUID)
              else:
                # TODO: those are not used at all
                logging.debug( "Found other reference")
                loadable.ReferencedOtherInstanceUIDs.append(refSOPSequence.ReferencedSOPInstanceUID)

      for segSeriesInstanceUID in loadable.ReferencedSegmentationInstanceUIDs[uid]:
        segLoadables = segPlugin.examine([slicer.dicomDatabase.filesForSeries(segSeriesInstanceUID)])
        for segLoadable in segLoadables:
          loadable.referencedInstanceUIDs += segLoadable.referencedInstanceUIDs

    loadable.referencedInstanceUIDs = list(set(loadable.referencedInstanceUIDs))

    if len(loadable.ReferencedSegmentationInstanceUIDs[uid])>1:
      logging.warning("SR references more than one SEG. This has not been tested!")
    for segUID in loadable.ReferencedSegmentationInstanceUIDs:
      loadable.referencedSegInstanceUIDs.append(segUID)

    if len(loadable.ReferencedRWVMSeriesInstanceUIDs)>1:
      logging.warning("SR references more than one RWVM. This has not been tested!")
    # not adding RWVM instances to referencedSeriesInstanceUIDs
    return loadable

def importDICOMSeries(self):
    indexer = ctk.ctkDICOMIndexer()
    db = slicer.dicomDatabase

    fileList = self.getFileList(self._intraopDataDir)

    newFileList = list(set(fileList) - set(self.currentFileList))

    for currentFile in newFileList:
      currentFile = os.path.join(self._intraopDataDir, currentFile)
      indexer.addFile(db, currentFile, None)
      series = self.makeSeriesNumberDescription(currentFile)
      if series and series not in self.seriesList and self.isDICOMSeriesEligible(series):
        self.seriesList.append(series)
        self.createLoadableFileListForSeries(series)

    indexer.addDirectory(db, self._intraopDataDir)
    indexer.waitForImportFinished()

def generateSlicenamesTextfile(ctDicomSeriesUID, slicenamesFilename, outputFolder):
  """ Generate slicenames.txt file, with list of ct dicom slices, in increasing slice order (IS direction)
  """
  filePaths = slicer.dicomDatabase.filesForSeries(ctDicomSeriesUID)
  if len(filePaths) == 0:
    logging.error('Failed to find files in DICOM database for UID ' + str(ctDicomSeriesUID))
    return False

  from DICOMLib import DICOMUtils
  unsortedFileList = slicer.dicomDatabase.filesForSeries(ctDicomSeriesUID)
  sortedFileList, distances, warnings = DICOMUtils.getSortedImageFiles(unsortedFileList)

  outFile = open(os.path.join(outputFolder, slicenamesFilename), "w")
  counter = 1
  numDicomFiles = len(sortedFileList)
  for sliceFileName in sortedFileList:
    outFile.write(sliceFileName)
    if counter != numDicomFiles:
      outFile.write("\n")
    counter += 1

def loadSeriesByFileName(self, filename):
    seriesUID = slicer.dicomDatabase.seriesForFile(filename)
    self.loadSeries(seriesUID)

def loadTestData(self, collection="MRHead",
                   uid="2.16.840.1.113662.4.4168496325.1025306170.548651188813145058"):
    if not len(slicer.dicomDatabase.filesForSeries(uid)):
      sampleData = TestDataLogic.downloadAndUnzipSampleData(collection)
      TestDataLogic.importIntoDICOMDatabase(sampleData['volume'])
    self.loadSeries(uid)
    masterNode = slicer.util.getNodesByClass('vtkMRMLScalarVolumeNode')[-1]
    tableNode = slicer.vtkMRMLTableNode()
    tableNode.SetAttribute("QuantitativeReporting", "Yes")
    slicer.mrmlScene.AddNode(tableNode)
    self.measurementReportSelector.setCurrentNode(tableNode)
    self.segmentEditorWidget.editor.setMasterVolumeNode(masterNode)
    self.retrieveTestDataButton.enabled = False