def capture_entire_page_screenshot(self,filename,kwargs):
self.do_command("<STR_LIT>", [filename,kwargs,])<EOL>
Saves the entire contents of the current window canvas to a PNG file.
Contrast this with the captureScreenshot command, which captures the
contents of the OS viewport (i.e. whatever is currently being displayed
on the monitor), and is implemented in the RC only. Currently this only
works in Firefox when running in chrome mode, and in IE non-HTA using
the EXPERIMENTAL "Snapsie" utility. The Firefox implementation is mostly
borrowed from the Screengrab! Firefox extension. Please see
http://www.screengrab.org and http://snapsie.sourceforge.net/ for
details.

'filename' is the path to the file to persist the screenshot as. No                  filename extension will be appended by default.                  Directories will not be created if they do not exist,                    and an exception will be thrown, possibly by native                  code.
'kwargs' is a kwargs string that modifies the way the screenshot                  is captured. Example: "background=#CCFFDD" .                  Currently valid options:
*    background
    the background CSS for the HTML document. This                     may be useful to set for capturing screenshots of                     less-than-ideal layouts, for example where absolute                     positioning causes the calculation of the canvas                     dimension to fail and a black background is exposed                     (possibly obscuring black text).