docs: def blob_counter(self):
          """Create a blob counter."""
          import aa    # pylint: disablF0401        # noqa
          from ROOT import EventFile    # pylint: disable F0401
  
          try:
              event_file = EventFile(self.filename)
          except Exception:
              raise SystemExit("Could not open file")
  
          num_blobs = 0
          for event in event_file:
              num_blobs += 1
  
          return num_blobs