Congratulations, you made it correctly! HOWEVER, if this string is used for the first time (as in, have you never used that string before [which means it isn't in the string table]) can cause the string table to become unsynchronized (it enters the string table for only one person), which can also lead to some desyncs:
JASS:
function Test takes nothing returns nothing
//this is the proper method
local string s = "war3mapImported\\FX.mdl"
if GetLocalPlayer() != Player(0) then
set s = ""
endif
call DestroyEffect(AddSpecialEffect(s,0.,0.))
endfunction
That is the proper method for creating effects locally.