Showing the dog a slightly different picture while leveraging what has already been established.
As a service dog, Raya needs to be socialized to all kinds of new things, including equipment her handler may use or will be using.
Having already established a heel while walking her, the chair is brought in slowly and she is shown that the same rules still apply, even if things look a little different (I move a little slower and less smoothly and am at her level, stop more often, make random turns and generally show somewhat different patterns). Her job is to apply what she already knows about how to walk appropriately to this new situation, and adapt as needed.