def __init__(self):
    self.style = color_style()

def create_parser(self, prog_name, subcommand):
    """
    Create and return the ``OptionParser`` which will be used to
    parse the arguments to this command.
    """
    return OptionParser(prog=prog_name,
                        usage=self.usage(subcommand),
                        version=self.get_version(),
                        option_list=self.option_list)

def execute(self, *args, **options):
    """
    Try to execute this command, performing model validation if
    needed (as controlled by the attribute
    ``self.requires_model_validation``, except if force-skipped).
    """
    self.stdout = OutputWrapper(options.get('stdout', sys.stdout))
    self.stderr = OutputWrapper(options.get('stderr', sys.stderr), self.style.ERROR)
    if self.can_import_settings:
        from django.conf import settings
    saved_locale = None
    if not self.leave_locale_alone:
        # Only mess with locales if we can assume we have a working
        # settings file, because django.utils.translation requires settings
        # (The final saying about whether the i18n machinery is active will be
        # found in the value of the USE_I18N setting)
        if not self.can_import_settings:
            raise CommandError("Incompatible values of 'leave_locale_alone' "
                               "(%s) and 'can_import_settings' (%s) command "
                               "options." % (self.leave_locale_alone,
                                             self.can_import_settings))
        # Switch to US English, because django-admin.py creates database
        # content like permissions, and those shouldn't contain any
        # translations.
        from django.utils import translation
        saved_locale = translation.get_language()
        translation.activate('en-us')
    try:
        if self.requires_model_validation and not options.get('skip_validation'):
            self.validate()
        output = self.handle(*args, **options)
        if output:
            if self.output_transaction:
                # This needs to be imported here, because it relies on
                # settings.
                from django.db import connections, DEFAULT_DB_ALIAS
                connection = connections[options.get('database', DEFAULT_DB_ALIAS)]
                if connection.ops.start_transaction_sql():
                    self.stdout.write(self.style.SQL_KEYWORD(connection.ops.start_transaction_sql()))
            self.stdout.write(output)
            if self.output_transaction:
                self.stdout.write('\n' + self.style.SQL_KEYWORD("COMMIT;"))
    finally:
        if saved_locale is not None:
            translation.activate(saved_locale)

def get_version(self):
    """
    Return the Django version, which should be correct for all
    built-in Django commands. User-supplied commands should
    override this method.
    """
    return django.get_version()

def handle(self, *args, **options):
    corpus_id = args[-1]
    corpus = MediaCorpus.objects.get(public_id=corpus_id)
    book = BaseEpubMixin()
    book.write_book(corpus)
    for collection in corpus.children.all():
        book = BaseEpubMixin()
        book.write_book(corpus, collection=collection)

def print_help(self, prog_name, subcommand):
    """
    Print the help message for this command, derived from
    ``self.usage()``.
    """
    parser = self.create_parser(prog_name, subcommand)
    parser.print_help()

def run_from_argv(self, argv):
    """
    Set up any environment changes requested (e.g., Python path
    and Django settings), then run this command. If the
    command raises a ``CommandError``, intercept it and print it sensibly
    to stderr. If the ``--traceback`` option is present or the raised
    ``Exception`` is not ``CommandError``, raise it.
    """
    parser = self.create_parser(argv[0], argv[1])
    options, args = parser.parse_args(argv[2:])
    handle_default_options(options)
    try:
        self.execute(*args, **options.__dict__)
    except Exception as e:
        if options.traceback or not isinstance(e, CommandError):
            raise
        # self.stderr is not guaranteed to be set here
        stderr = getattr(self, 'stderr', OutputWrapper(sys.stderr, self.style.ERROR))
        stderr.write('%s: %s' % (e.__class__.__name__, e))
        sys.exit(1)

def usage(self, subcommand):
    """
    Return a brief description of how to use this command, by
    default from the attribute ``self.help``.
    """
    usage = '%%prog %s [options] %s' % (subcommand, self.args)
    if self.help:
        return '%s\n\n%s' % (usage, self.help)
    else:
        return usage

def validate(self, app=None, display_num_errors=False):
    """
    Validates the given app, raising CommandError for any errors.
    If app is None, then this will validate all installed apps.
    """
    from django.core.management.validation import get_validation_errors
    s = StringIO()
    num_errors = get_validation_errors(s, app)
    if num_errors:
        s.seek(0)
        error_text = s.read()
        raise CommandError("One or more models did not validate:\n%s" % error_text)
    if display_num_errors:
        self.stdout.write("%s error%s found" % (num_errors, '' if num_errors == 1 else 's'))