copy( euler ) {

		this._x = euler._x;
		this._y = euler._y;
		this._z = euler._z;
		this._order = euler._order;

		this._onChangeCallback();

		return this;

	}
Copies the values of the given Euler instance to this instance.

@param {Euler} euler - The Euler instance to copy.
@return {Euler} A reference to this Euler instance.