|Meta Data Provider:||
Allows to set a constraint regarding the layer placement of a node. Let i be the value of teh constraint. Assumed the drawing has n layers and i < n. If set to i, it expresses that the node should be placed in i-th layer. Should i>=n be true then the node is placed in the last layer of the drawing. Note that this option is not part of any of ELK Layered’s default configurations but is only evaluated as part of the
InteractiveLayeredGraphVisitor, which must be applied manually or used via the `DiagramLayoutEngine.