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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 _clean_dict(row):
 """ Transform empty strings values of dict `row` to None. """

    row_cleaned = {}
    for key, val in row.items():
        if val is None or val == '':
            row_cleaned[key] = None
        else:
            row_cleaned[key] = val
    return row_cleaned