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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 patch(self, force=False):
 """Patch local_settings.py.example with local_settings.diff. The patch application generates the local_settings.py file (the local_settings.py.example remains unchanged). http://github.com/sitkatech/pypatch fails if the local_settings.py.example file is not 100% identical to the one used to generate the first diff so we use the patch command instead. """


        with DirContext(self.local_settings_dir) as dircontext:
            if os.path.exists(self.local_settings_diff):
                if not os.path.exists(self.local_settings_file) or force:
                    local_settings_reject = \
                        self.local_settings_reject_pattern % (
                            time.strftime(self.file_time_fmt, time.localtime())
                        )
                    patch_cmd = shlex.split(
                        'patch %s %s -o %s -r %s' % (
                            self.local_settings_example,
                            self.local_settings_diff,
                            self.local_settings_file,
                            local_settings_reject
                        )
                    )
                    try:
                        subprocess.check_call(patch_cmd)
                    except subprocess.CalledProcessError:
                        if os.path.exists(local_settings_reject):
                            sys.exit(
                                'Some conflict(s) occurred. Please check "%s" '
                                'to find unapplied parts of the diff.\n'
                                'Once conflicts are solved, it is safer to '
                                'regenerate a newer diff with the "--gendiff" '
                                'option.' %
                                os.path.join(
                                    dircontext.curdir,
                                    local_settings_reject)
                            )
                        else:
                            sys.exit('An unhandled error occurred.')
                    print('Generation of "%s" successful.' % os.path.join(
                        dircontext.curdir,
                        self.local_settings_file)
                    )
                    sys.exit(0)
                else:
                    sys.exit(
                        '"%s" already exists.' %
                        os.path.join(dircontext.curdir,
                                     self.local_settings_file)
                    )
            else:
                sys.exit('No diff file found, please generate one with the '
                         '"--gendiff" option.')