how to get developer email using access entity and set this in a header

[rohanjangid]

i have an proxy with simply endpoint of https://mocktarget.apigee.net/json and inside this proxy i added a access entity policy and inside this policy what i wrote so i can get developer mail id in body whenever anyone hit on api

this is my access entity policy

here i am extract variable

here i am using assign message policy

and here is the result

and here is the result when i hit api "{"fault":{"faultstring":"AccessEntity.GetDeveloperProfile message is not available for ExtractVariable: SetDeveloperProfile","detail":{"errorcode":"steps.extractvariables.SourceMessageNotAvailable"}}}"

please let me know where i made mistake