def get_cube_diff(cube_1, cube_2):
    """
    Take the difference of two Iris data cubes. 
    Computed as cube_1 - cube_2.
    
    Parameters
    ----------
    cube_1 : Iris cube.
    cube_2 : Iris cube.
    
    Return
    ------
    Iris cube containing the difference of cube_1 - cube_2
    """
    diff_cube = cube_1 - cube_2
    return diff_cube