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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 _get_config(filename):
 """ Parse the provided YAML file and return a dict. :parse filename: A string containing the path to YAML file. :return: dict """

    i = interpolation.Interpolator(interpolation.TemplateWithDefaults,
                                   os.environ)

    with open(filename, 'r') as stream:
        try:
            interpolated_config = i.interpolate(stream.read())
            return yaml.safe_load(interpolated_config)
        except yaml.parser.ParserError as e:
            msg = 'Error parsing gilt config: {0}'.format(e)
            raise ParseError(msg)