As you can see, Drake wants to execute the step again! However, now mentions a
different reason, namely, that there is no input step *\[no-input-step\]*. Its
default behavior is to check whether the input has changed by looking at the
timestamp of the input. However, since we didn't specify any input, Drake
doesn't know whether or not this step should be run again. We can disable this
default behavior to check timestamps as follows:
