One of "right", "left", "top", "bottom" (outside
the plotting area), "topleft", "topright", "topmiddle",
"bottomleft", "bottomright", or "bottommiddle" (inside the plotting
area).
style
One of "white", "light", "dark_blue", or "dark_gray".
"white" sets the background to white, "light" to light gray,
"dark_gray" to dark gray, "dark_blue" to dark blue.