'Create a new BarChartStyle.
Args:
bar_thickness: The thickness of a bar, in pixels. Set this to None if
you want the bar thickness to be auto-calculated (this is the default
behaviour).
bar_gap: The gap between bars, in pixels. Default is 4.
group_gap: The gap between groups of bars, in pixels. Default is 8.'

def __init__(self, bar_thickness=None, bar_gap=_DEFAULT_BAR_GAP, group_gap=_DEFAULT_GROUP_GAP, use_fractional_gap_spacing=False):

    self.bar_thickness = bar_thickness
    self.bar_gap = bar_gap
    self.group_gap = group_gap
    self.use_fractional_gap_spacing = use_fractional_gap_spacing
