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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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