code: def get_monolayer(self):
          
  
          unit_a = self.get_unit_primitive_area
          Nsurfs = self.Nsurfs_ads_in_slab
          Nads = self.Nads_in_slab
          return Nads / (unit_a * Nsurfs)
docs: Returns the primitive unit surface area density of the
              adsorbate.