code: def missing_particle(separation=0.0, radius=RADIUS, SNR=20):
      
      # create a base image of one particle
      s = init.create_two_particle_state(imsize=6*radius+4, axis='x', sigma=1.0/SNR,
              delta=separation, radius=radius, stateargs={'varyn': True}, psfargs={'error': 1e-6})
      s.obj.typ[1] = 0.
      s.reset()
  
      return s, s.obj.pos.copy()
docs: create a two particle state and compare it to featuring using a single particle guess