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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 prepare_package(err, path, expectation=0, for_appversions=None, timeout=-1):
 """Prepares a file-based package for validation. timeout is the number of seconds before validation is aborted. If timeout is -1 then no timeout checking code will run. """


    package = None
    try:
        # Test that the package actually exists. I consider this Tier 0
        # since we may not even be dealing with a real file.
        if not os.path.isfile(path):
            err.error(('main', 'prepare_package', 'not_found'),
                      'The package could not be found')
            return

        # Pop the package extension.
        package_extension = os.path.splitext(path)[1]
        package_extension = package_extension.lower()

        def timeout_handler(signum, frame):
            raise validator.ValidationTimeout(timeout)

        if timeout != -1:
            signal.signal(signal.SIGALRM, timeout_handler)
            signal.setitimer(signal.ITIMER_REAL, timeout)

        if package_extension == '.xml':
            test_search(err, path, expectation)
        elif package_extension not in ('.xpi', '.jar'):
            err.error(('main', 'prepare_package', 'unrecognized'),
                      'The package is not of a recognized type.')
        else:
            package = open(path, 'rb')
            test_package(err, package, path, expectation, for_appversions)

        err.metadata['is_extension'] = err.detected_type == PACKAGE_EXTENSION

    except validator.ValidationTimeout:
        err.system_error(
            msg_id='validation_timeout',
            message='Validation has timed out',
            signing_severity='high',
            description=('Validation was unable to complete in the allotted '
                         'time. This is most likely due to the size or '
                         'complexity of your add-on.',
                         'This timeout has been logged, but please consider '
                         'filing an issue report here: '
                         'https://bit.ly/1POrYYU'),
            exc_info=sys.exc_info())

    except Exception:
        err.system_error(exc_info=sys.exc_info())

    finally:
        # Remove timers and signal handlers regardless of whether
        # we've completed successfully or the timer has fired.
        if timeout != -1:
            signal.setitimer(signal.ITIMER_REAL, 0)
            signal.signal(signal.SIGALRM, signal.SIG_DFL)

        if package:
            package.close()

        decorator.cleanup()