def get_pyramid_single(xyz):
    """Determine to which out of six pyramids in the cube a (x, y, z)
    coordinate belongs.

    Parameters
    ----------
    xyz : numpy.ndarray
        1D array (x, y, z) of 64-bit floats.

    Returns
    -------
    pyramid : int
        Which pyramid `xyz` belongs to as a 64-bit integer.

    Notes
    -----
    This function is optimized with Numba, so care must be taken with
    array shapes and data types.
    """
    x, y, z = xyz
    x_abs, y_abs, z_abs = abs(x), abs(y), abs(z)
    if (x_abs <= z) and (y_abs <= z):  # Top
        return 1
    elif (x_abs <= -z) and (y_abs <= -z):  # Bottom
        return 2
    elif (z_abs <= x) and (y_abs <= x):  # Front
        return 3
    elif (z_abs <= -x) and (y_abs <= -x):  # Back
        return 4
    elif (x_abs <= y) and (z_abs <= y):  # Right
        return 5
    else:  # (x_abs <= -y) and (z_abs <= -y)  # Left
        return 6