TypeError: unsupported operand type(s) for >>: 'CenteredGrid' and 'StaggeredGrid' in Navier-Stokes Forward Simulation

[topsy404]

Thanks for the wonderful work with vivid examples.
When I try to run the Navier-Stokes Forward Simulation demo, I got the following error.

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-4-6c1e44e4d5ef> in <module>()
      7     return velocity, smoke, pressure
      8 
----> 9 velocity, smoke, pressure = step(velocity, smoke, None, dt=DT)
     10 
     11 print("Max. velocity and mean marker density: " + format( [ math.max(velocity.values) , math.mean(smoke.values) ] ))

<ipython-input-4-6c1e44e4d5ef> in step(velocity, smoke, pressure, dt, buoyancy_factor)
      1 def step(velocity, smoke, pressure, dt=1.0, buoyancy_factor=1.0):
      2     smoke = advect.semi_lagrangian(smoke, velocity, dt) + INFLOW
----> 3     buoyancy_force = smoke * (0, buoyancy_factor) >> velocity  # resamples smoke to velocity sample points
      4     velocity = advect.semi_lagrangian(velocity, velocity, dt) + dt * buoyancy_force
      5     velocity = diffuse.explicit(velocity, NU, dt)

TypeError: unsupported operand type(s) for >>: 'CenteredGrid' and 'StaggeredGrid'

What do the >> mean here?

[topsy404]

fixed by this commit.