No module named 'strawberryfields.circuitspecs'

[kyeteraydeniz]

The sfopenboson plugin in Forced quantum harmonic oscillator tutorial here gives the following error

---------------------------------------------------------------------------
ModuleNotFoundError                       Traceback (most recent call last)
<ipython-input-3-c0d26999d831> in <module>()
      2 import strawberryfields as sf
      3 from strawberryfields.ops import *
----> 4 from sfopenboson.ops import GaussianPropagation

/anaconda3/lib/python3.6/site-packages/sfopenboson/ops.py in <module>()
     95 from strawberryfields.backends.shared_ops import sympmat
     96 
---> 97 from strawberryfields.circuitspecs import GaussianSpecs, FockSpecs, TFSpecs
     98 
     99 from .auxillary import trotter_layer, quadratic_coefficients

ModuleNotFoundError: No module named 'strawberryfields.circuitspecs'

when from sfopenboson.ops import GaussianPropagation is imported.