placeholder function added to model

Model.py

@@ -348,6 +348,9 @@ class Model:
             FCa_0,  # FCa
         ]
 
+    def calculated_current():
+        return None
+
     def solve(self, initial_values, tspan, dt, times):
         times = np.arange(*tspan, dt)
 

fitter.py

@@ -65,7 +65,7 @@ class Fitter:
             times=self.time_points,
             tspan=self.tspan,
             dt=self.dt,
-            initial_values=self.initial_values,
+            initial_values=self.initial_values
         )
 
         _calc_curr = model.calculated_current()