* @param newModel * @returns {Model}

* Recursive function to calculate intersection and complement paths in 2 given pathsets at a given depth. * * Parameters: * - requestedPath: full

* Create a new array consistent of a1 plus an additional element. Avoids the unnecessary array allocation when using `a1.concat([element])`.

* Create a new array consisting of a1 + a subset of a2. Avoids allocating an extra array by calling `slice` on a2.

* Create a new array consisting of a1 + a2 + a subset of a3. Avoids allocating an extra array by calling `slice` on a3.

* allUnique * return true if every number in an array is unique

* Create a unique hash key for a set * of paths