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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 ApproximateDistanceBetweenPoints(pa, pb):
 """Finds the distance between two points on the Earth's surface. This is an approximate distance based on assuming that the Earth is a sphere. The points are specified by their lattitude and longitude. Args: pa: the first (lat, lon) point tuple pb: the second (lat, lon) point tuple Returns: The distance as a float in metres. """

  alat, alon = pa
  blat, blon = pb
  sa = transitfeed.Stop(lat=alat, lng=alon)
  sb = transitfeed.Stop(lat=blat, lng=blon)
  return transitfeed.ApproximateDistanceBetweenStops(sa, sb)