[tutorial_projection] mention parameter handling again

docs/source/tutorial_projection.rst

@@ -96,10 +96,10 @@ outputs or error estimates. Next, we take a look at the implemenation of
     print_source(fom.compute)
 
 What we see is a default implementation from :class:`~pymor.models.interface.Model` that
-takes care of :mod:`caching <pymor.core.cache>` and :mod:`logging <pymor.core.logger>`,
-but defers the actual computations to further private methods. Implementors can directly implement
-:meth:`~pymor.models.interface.Model._compute` to compute multiple return values
-at once in an optimized way. Our given model, however, just implements 
+takes care of checking the input |parameter values| `mu`, :mod:`caching <pymor.core.cache>` and
+:mod:`logging <pymor.core.logger>`, but defers the actual computations to further private methods.
+Implementors can directly implement :meth:`~pymor.models.interface.Model._compute` to compute
+multiple return values at once in an optimized way. Our given model, however, just implements 
 :meth:`~pymor.models.interface.Model._compute_solution` where we can find the
 actual code: