code: def centroid(poly):
      
      f_total = 0
      x_total = 0
      y_total = 0
      # TODO: polygon holes at coordinates[1]
      points = poly['coordinates'][0]
      j = len(points) - 1
      count = len(points)
  
      for i in range(0, count):
          p1_x = points[i][1]
          p1_y = points[i][0]
          p2_x = points[j][1]
          p2_y = points[j][0]
  
          f_total = p1_x * p2_y - p2_x * p1_y
          x_total += (p1_x + p2_x) * f_total
          y_total += (p1_y + p2_y) * f_total
          j = i
  
      six_area = area(poly) * 6
      return {'type': 'Point', 'coordinates': [y_total / six_area, x_total / six_area]}
docs: get the centroid of polygon
      adapted from http://paulbourke.net/geometry/polyarea/javascript.txt
  
      Keyword arguments:
      poly -- polygon geojson object
  
      return polygon centroid