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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(cls, key, default=None, separator='.', global_=False):
 """ Retrieve a key value from loaded configuration. Order of search if global_=False: 1/ environnment variables 2/ local configuration 3/ global configuration """

        # first check environnment variables
        # if we're not in global scope
        if not global_:
            ret = os.environ.get(key.upper().replace('.', '_'))
            if ret is not None:
                return ret

        # then check in local and global configuration unless global_=True
        scopes = ['global'] if global_ else ['local', 'global']
        for scope in scopes:
            ret = cls._get(scope, key, default, separator)
            if ret is not None and ret != default:
                return ret

        if ret is None or ret == default:
            return default