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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def inspect(logdir='', event_file='', tag=''):
 """Main function for inspector that prints out a digest of event files. Args: logdir: A log directory that contains event files. event_file: Or, a particular event file path. tag: An optional tag name to query for. Raises: ValueError: If neither logdir and event_file are given, or both are given. """

  print(PRINT_SEPARATOR +
        'Processing event files... (this can take a few minutes)\n' +
        PRINT_SEPARATOR)
  inspection_units = get_inspection_units(logdir, event_file, tag)

  for unit in inspection_units:
    if tag:
      print('Event statistics for tag {} in {}:'.format(tag, unit.name))
    else:
      # If the user is not inspecting a particular tag, also print the list of
      # all available tags that they can query.
      print('These tags are in {}:'.format(unit.name))
      print_dict(get_unique_tags(unit.field_to_obs))
      print(PRINT_SEPARATOR)
      print('Event statistics for {}:'.format(unit.name))

    print_dict(get_dict_to_print(unit.field_to_obs), show_missing=(not tag))
    print(PRINT_SEPARATOR)