Asserts Real input value while passing it through to Real output.
Level of assertion message can be selected. Error will directly abort the simulation.
  As during a period after initialization one might not want to assert
  the Real value, the parameter startTime can be set.
  Use startTime =
  Modelica.Constants.inf to totally avoid assertion
  (functionality then is the same as in Modelica.Blocks.Routing.RealPassThrough).