Design a Python function that can append or increment a number in a string.
This task resembles file-naming practices where numerically ended file names are incremented to avoid duplication. Develop a function named `increment_string_suffix` which receives a string `input_str`. If `input_str` terminates with a number, increment that number by 1. If not, add '1' to `input_str`. Note: The function assumes that `input_str` only consists of alphanumeric characters. ### Parameters - `input_str`: A string which could end with a numeric value. ### Return Value - Returns a string, either appended with '1' or with its ending number incremented by 1. ### Examples ```python # 'word519' ends with 519. After incrementing, it becomes 'word520' increment_string_suffix('word519') # 'word520' # 'word99' ends with 99. After incrementing, it becomes 'word100' increment_string_suffix('word99') # 'word100' # 'word' doesn't end with a number, hence, append '1' increment_string_suffix('word') # 'word1' ```