If we do not have this little dummy function with the plot command in the example,
then 'R CMD check' in buildTDMR.r will fail when the examples are checked.
The reason: The file TDMR.Rcheck/TDMR-Ex.R contains a footer which tries to
close a graphics device with grDevices::dev.off(). But if there is no graphics device
from the previous example, dev.off() tries to operate on the null device and this
produces an error.