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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 _default_ctx(self):
 """ Return the package config or context and normalize some of the values """

        if not self.in_app_directory:
            print("Warning: {} does not exist. Using the default.".format(
                self.package))
            ctx = {}

        else:
            with open(self.package) as f:
                ctx = dict(yaml.load(f, Loader=yaml.RoundTripLoader))

        if self.in_app_directory:
            # Update the env for each platform
            excluded = list(ctx.get('excluded', []))

            for env in [ctx['ios'], ctx['android']]:
                if 'python_build_dir' not in env:
                    env['python_build_dir'] = expanduser(abspath('build/python'))
                if 'conda_prefix' not in env:
                    env['conda_prefix'] = os.environ.get(
                        'CONDA_PREFIX', expanduser(abspath('venv')))

                # Join the shared and local exclusions
                env['excluded'] = list(env.get('excluded', [])) + excluded

        return ctx