docs: public void setLossVariables(String... lossVariableNames){
          this.lossVariables.clear();
          for(String s : lossVariableNames){
              addLossVariable(s);
          }
          //After changing loss function variables, we (probably) need to recreate gradient function - as gradient
          // function is defined with respect to specific loss function variables
          sameDiffFunctionInstances.remove("grad");
      }