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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 _bits_to_float(bits, lower=-90.0, middle=0.0, upper=90.0):
 """Convert GeoHash bits to a float."""

  for i in bits:
    if i:
      lower = middle
    else:
      upper = middle
    middle = (upper + lower) / 2
  return middle