treemap.paddingLeft()

treemap.paddingLeft([padding])

If padding is specified, sets the left padding to the specified number or function and returns this treemap layout. If padding is not specified, returns the current left padding function, which defaults to the constant zero. If padding is a function, it is invoked for each node with children, being passed the current node. The left padding is used to separate the left edge of a node from its children.