In many of the responses from linkedIn, _key is used to repeat back to the calling party information about the request.  For example, in the search by email call _key is used to repeat back the input email (if it was matched).  In that scenario (as you can see in the cassettes) only two fields are presented back _key which you use to validate that an email was found, and ID.  I ran all the tests and it appears that with that conversion out everything still passes.  In addition, most of the responses back from linkedIn seem to contain ID with the data we'd expect.

I hesitated long on this but feel its the best way to preserve this data without appending another response value and copying the existing data.