Factor graph:
size: 5
factor 0: BetweenFactor(1,2)
  measured(2, 0, 0)
  noise model: diagonal sigmas [0.2; 0.2; 0.1];
factor 1: BetweenFactor(2,3)
  measured(2, 0, 0)
  noise model: diagonal sigmas [0.2; 0.2; 0.1];
factor 2: keys = { 1 }
  noise model: diagonal sigmas [0.1; 0.1];
factor 3: keys = { 2 }
  noise model: diagonal sigmas [0.1; 0.1];
factor 4: keys = { 3 }
  noise model: diagonal sigmas [0.1; 0.1];