code: def update(self, iterations=10):
          
              
          
          # The graph fades in when initially constructed.
          self.alpha += 0.05
          self.alpha = min(self.alpha, 1.0)
  
          # Iterates over the graph's layout.
          # Each step the graph's bounds are recalculated
          # and a number of iterations are processed,
          # more and more as the layout progresses.
          if self.layout.i == 0:
              self.layout.prepare()
              self.layout.i += 1
          elif self.layout.i == 1:
              self.layout.iterate()
          elif self.layout.i < self.layout.n:
              n = min(iterations, self.layout.i / 10 + 1)
              for i in range(n): 
                  self.layout.iterate()
          
          # Calculate the absolute center of the graph.
          min_, max = self.layout.bounds
          self.x = _ctx.WIDTH - max.x*self.d - min_.x*self.d
          self.y = _ctx.HEIGHT - max.y*self.d - min_.y*self.d
          self.x /= 2
          self.y /= 2
              
          return not self.layout.done
docs: Iterates the graph layout and updates node positions.