Goal: Pan the camera.

Code:

camera = Graphics.Camera
up_vector = camera.UpVector
view_vector = camera.ViewVector

#get the 2D CSYS in the screen plane based on the computed UpVector, derived from the prescribed one.
plane_right = up_vector.CrossProduct(view_vector)                        # the “x” axis of the 2D CSYS.
plane_up = up_vector - (up_vector.DotProduct(view_vector)) * view_vector # the “y” axis of the 2D CSYS.

#construct the pan vector in the screen plane (Use the units from Graphics.Unit).
pan_right = 100
pan_up = 100
pan_vector = plane_right * pan_right + plane_up * pan_up 

#set the new focal point by adding the pan vector to the original focal point.
pan_origin = camera.FocalPoint.Location
new_x, new_y, new_z = (pan_origin[0] + pan_vector[0], pan_origin[1] + pan_vector[1], pan_origin[2] + pan_vector[2])
camera.FocalPoint = Point([new_x, new_y, new_z], Graphics.Unit)