def highlight_region(plt, start_x, end_x):
start_x = convert_to_mdate(start_x)<EOL>end_x = convert_to_mdate(end_x)<EOL>plt.axvspan(start_x, end_x, color=CONSTANTS.HIGHLIGHT_COLOR, alpha=CONSTANTS.HIGHLIGHT_ALPHA)<EOL>
Highlight a region on the chart between the specified start and end x-co-ordinates.
param pyplot plt: matplotlibk pyplot which contains the charts to be highlighted
param string start_x : epoch time millis
param string end_x : epoch time millis