Generate graph from the data.

        Example for the mem plugin:
        {'percent': [
            (datetime.datetime(2018, 3, 24, 16, 27, 47, 282070), 51.8),
            (datetime.datetime(2018, 3, 24, 16, 27, 47, 540999), 51.9),
            (datetime.datetime(2018, 3, 24, 16, 27, 50, 653390), 52.0),
            (datetime.datetime(2018, 3, 24, 16, 27, 53, 749702), 52.0),
            (datetime.datetime(2018, 3, 24, 16, 27, 56, 825660), 52.0),
            ...
            ]
        }

        Return:
        * True if the graph have been generated
        * False if the graph have not been generated

def export(self, title, data):
        """Generate graph from the data.

        Example for the mem plugin:
        {'percent': [
            (datetime.datetime(2018, 3, 24, 16, 27, 47, 282070), 51.8),
            (datetime.datetime(2018, 3, 24, 16, 27, 47, 540999), 51.9),
            (datetime.datetime(2018, 3, 24, 16, 27, 50, 653390), 52.0),
            (datetime.datetime(2018, 3, 24, 16, 27, 53, 749702), 52.0),
            (datetime.datetime(2018, 3, 24, 16, 27, 56, 825660), 52.0),
            ...
            ]
        }

        Return:
        * True if the graph have been generated
        * False if the graph have not been generated
        """
        if data == {}:
            return False

        chart = DateTimeLine(title=title.capitalize(),
                             width=self.width,
                             height=self.height,
                             style=self.style,
                             show_dots=False,
                             legend_at_bottom=True,
                             x_label_rotation=20,
                             x_value_formatter=lambda dt: dt.strftime('%Y/%m/%d %H:%M:%S'))
        for k, v in iteritems(time_serie_subsample(data, self.width)):
            chart.add(k, v)
        chart.render_to_file(os.path.join(self.path,
                                          title + '.svg'))
        return True