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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_abbreviations(input_string, output_length=0):
 """ Generates abbreviations for input_string :param input_string: str, name of object :param output_length: int, optional specific length of abbreviations, default is off :return: list(str), list of all combinations that include the first letter (possible abbreviations) """

        for i, j in itertools.combinations(range(len(input_string[1:]) + 1), 2):
            abbr = input_string[0] + input_string[1:][i:j]
            if len(abbr) >= output_length:
                yield abbr
            elif output_length == 0:
                yield abbr
        # Have to add the solitary letter as well
        if not output_length or output_length == 1:
            yield input_string[0]