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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_result(self):
 """Perform the call and return the graph data :return: Encoded PNG graph data string to be inserted in a `src` atribute of a HTML img tag. """

        png = self.call()
        if png is None:
            return
        if png.startswith('GD extension must be loaded'):
            current_plugin.logger.warning('Piwik server answered on ImageGraph.get: %s', png)
            return
        return 'data:image/png;base64,{}'.format(b64encode(png))