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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 _find_first_of(line, substrings):
 """Find earliest occurrence of one of substrings in line. Returns pair of index and found substring, or (-1, None) if no occurrences of any of substrings were found in line. """

    starts = ((line.find(i), i) for i in substrings)
    found = [(i, sub) for i, sub in starts if i != -1]
    if found:
        return min(found)
    else:
        return -1, None