is an option for legends that specifies an overall label for a legend.
- LegendLabel->None specifies that no label should be given.
- LegendLabel->Placed[lbl, pos, fun] puts lbl with fun applied at the position specified by pos.
- When the label position is Bottom, Top, Left, or Right, the label will be inside any structure created by LegendFunction.
- When the label position is , , , or , the label will be outside any structure created by LegendFunction.
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