specifying identity file for scp within tramp

[锁住子]

Can anyone tell me if it's possible to direct tramp to use a
particular set of ssh keys when connecting to a particular server? I'm
trying to use scp with the equivalent of the -i option, what I tried
below just seems to confuse tramp, is there some other way I should be
doing this?

(add-to-list 'tramp-default-method-alist
              '("remote_server" "" "scp -i /Users/my_user/.ssh/
my_key"))


Thanks,
Eric