Clarify end of update function with comments

Added comments to clarify the end of the update function.

Author: MarkMelotto

book/2_modelling_advanced_ewatercycle/hbv_bmi.py

@@ -149,6 +149,12 @@ def update(self) -> None:
                 # Advance the model time by one step
                 self.current_timestep += 1
 
+###############################################################################    
+
+    "End of the update function!"
+
+############################################################################### 
+
     def set_pars(self, par) -> None:
         self.I_max  = par[0]                # maximum interception
         self.Ce     = par[1]                # Ea = Su / (sumax * Ce) * Ep
@@ -499,4 +505,4 @@ def load_var(ncfile: str | Path, varname: str) -> xr.DataArray:
         if data[varname].attrs['units'] == 'kg m-2 s-1':
             data[varname] = data[varname] * 24 * 3600 #mm/day
             #data[varname].attrs['units'] = 'mm d-1' TODO, fix.
-    return data[varname]
+    return data[varname]