code: def findCells(fnames):
      
      IDs=[]
      filesByExt = filesByExtension(fnames)
      for abfFname in filesByExt['abf']:
          ID=os.path.splitext(abfFname)[0]
          for picFname in filesByExt['jpg']+filesByExt['tif']:
              if picFname.startswith(ID):
                  IDs.append(ID)
                  break
      return smartSort(IDs)
docs: given a list of files, return a list of cells by their ID.
      A cell is indicated when an ABF name matches the start of another file.
      
      Example:
          123456.abf
          123456-whatever.tif