code: def _model_sanity(model):
          
          if not isinstance(model, ODEModel) and not isinstance(model, BaseNumericalModel):
              # Such a model should probably not contain derivatives
              for var, expr in model.items():
                  if isinstance(var, sympy.Derivative) or expr.has(sympy.Derivative):
                      warnings.warn(RuntimeWarning(
                          'The model contains derivatives in its definition. '
                          'Are you sure you don\'t mean to use `symfit.ODEModel`?'
                      ))
docs: Perform some basic sanity checking on the model to warn users when they
          might be trying something ill advised.
  
          :param model: model instance.