Saves a screenshot of the current window to a PNG image file. Returns
           False if there is any IOError, else returns True. Use full paths in
           your filename.

        :Args:
         - filename: The full path you wish to save your screenshot to. This
           should end with a `.png` extension.

        :Usage:
            ::

                driver.get_screenshot_as_file('/Screenshots/foo.png')

def get_screenshot_as_file(self, filename):
        """
        Saves a screenshot of the current window to a PNG image file. Returns
           False if there is any IOError, else returns True. Use full paths in
           your filename.

        :Args:
         - filename: The full path you wish to save your screenshot to. This
           should end with a `.png` extension.

        :Usage:
            ::

                driver.get_screenshot_as_file('/Screenshots/foo.png')
        """
        if not filename.lower().endswith('.png'):
            warnings.warn("name used for saved screenshot does not match file "
                          "type. It should end with a `.png` extension", UserWarning)
        png = self.get_screenshot_as_png()
        try:
            with open(filename, 'wb') as f:
                f.write(png)
        except IOError:
            return False
        finally:
            del png
        return True