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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 take_screeshot(self):
		'''
		Take a screenshot of the virtual viewport content.

		Return value is a png image as a bytestring.
		'''
		resp = self.Page_captureScreenshot()
		assert 'result' in resp
		assert 'data' in resp['result']
		imgdat = base64.b64decode(resp['result']['data'])
		return imgdat