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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 cutoff_filename(prefix, suffix, input_str):
 """ Cuts off the start and end of a string, as specified by 2 parameters Parameters prefix : string, if input_str starts with prefix, will cut off prefix suffix : string, if input_str end with suffix, will cut off suffix input_str : the string to be processed Returns ------- A string, from which the start and end have been cut """

    if prefix is not '':
        if input_str.startswith(prefix):
            input_str = input_str[len(prefix):]
    if suffix is not '':
        if input_str.endswith(suffix):
            input_str = input_str[:-len(suffix)]
    return input_str