'Format the chart by setting the min/max values on its dependent axis.'

def __call__(self, chart):

    if (not chart.data):
        return
    (min_value, max_value) = chart.GetMinMaxValues()
    if (None in (min_value, max_value)):
        return
    for axis in chart.GetDependentAxes():
        if (axis.min is not None):
            min_value = axis.min
        if (axis.max is not None):
            max_value = axis.max
    buffer = ((max_value - min_value) * self.buffer)
    for axis in chart.GetDependentAxes():
        if (axis.min is None):
            axis.min = (min_value - buffer)
        if (axis.max is None):
            axis.max = (max_value + buffer)
