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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 _next_lowest_integer(group_keys):
 """ returns the lowest available integer in a set of dict keys """

    try: #TODO Replace with max default value when dropping compatibility with Python < 3.4
        largest_int= max([ int(val) for val in group_keys if _is_int(val)])
    except:
        largest_int= 0
    return largest_int + 1