<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def iter_xCharts(self):
 """ Generate each xChart child element in document. """

        plot_tags = (
            qn('c:area3DChart'), qn('c:areaChart'), qn('c:bar3DChart'),
            qn('c:barChart'), qn('c:bubbleChart'), qn('c:doughnutChart'),
            qn('c:line3DChart'), qn('c:lineChart'), qn('c:ofPieChart'),
            qn('c:pie3DChart'), qn('c:pieChart'), qn('c:radarChart'),
            qn('c:scatterChart'), qn('c:stockChart'), qn('c:surface3DChart'),
            qn('c:surfaceChart')
        )

        for child in self.iterchildren():
            if child.tag not in plot_tags:
                continue
            yield child