Has PBC

import molsysmt as msm
from molsysmt import pyunitwizard as puw
import numpy as np

box = puw.quantity(2.0*np.identity(3), 'nm')
molsys = msm.build.make_water_box(box)

msm.pbc.has_pbc(molsys)

True

msm.set(molsys, box=None)

msm.pbc.has_pbc(molsys)

False