code: def indexOf(a, b):
      "Return the first index of b in a."
      for i, j in enumerate(a):
          if j == b:
              return i
      else:
          raise ValueError('sequence.index(x): x not in sequence'f indexOf(a, b):
      "Return the first index of b in a."
      for i, j in enumerate(a):
          if j == b:
              return i
      else:
          raise ValueError('sequence.index(x): x not in sequence')
docs: Return the first index of b in a.