Overlays `array1` onto `array2` with `alpha` blending.

    Args:
        array1: The first numpy array.
        array2: The second numpy array.
        alpha: The alpha value of `array1` as overlayed onto `array2`. This value needs to be between [0, 1],
            with 0 being `array2` only to 1 being `array1` only (Default value = 0.5).

    Returns:
        The `array1`, overlayed with `array2` using `alpha` blending.

def overlay(array1, array2, alpha=0.5):
    """Overlays `array1` onto `array2` with `alpha` blending.

    Args:
        array1: The first numpy array.
        array2: The second numpy array.
        alpha: The alpha value of `array1` as overlayed onto `array2`. This value needs to be between [0, 1],
            with 0 being `array2` only to 1 being `array1` only (Default value = 0.5).

    Returns:
        The `array1`, overlayed with `array2` using `alpha` blending.
    """
    if alpha < 0. or alpha > 1.:
        raise ValueError("`alpha` needs to be between [0, 1]")
    if array1.shape != array2.shape:
        raise ValueError('`array1` and `array2` must have the same shapes')

    return (array1 * alpha + array2 * (1. - alpha)).astype(array1.dtype)