init
Description:
Initializes a Euler using the given angles.
The order of the rotations is graphene_euler_order_default.
Parameters:
| this | the Euler to initialize | 
| x | rotation angle on the X axis, in degrees | 
| y | rotation angle on the Y axis, in degrees | 
| z | rotation angle on the Z axis, in degrees | 
Returns:
| the initialized Euler |