margins (margins) {
        if (!arguments.length) {
            return this._margin;
        }
        this._margin = margins;
        return this;
    }
Get or set the margins for a particular coordinate grid chart instance. The margins is stored as
an associative Javascript array.
@memberof MarginMixin
@instance
@example
var leftMargin = chart.margins().left; // 30 by default
chart.margins().left = 50;
leftMargin = chart.margins().left; // now 50
@param {{top: Number, right: Number, left: Number, bottom: Number}} [margins={top: 10, right: 50, bottom: 30, left: 30}]
@returns {{top: Number, right: Number, left: Number, bottom: Number}|MarginMixin}