tA = {...}
eT = {}
-- "event_type":"send_message"
for k,v in ipairs(tA) do
 f=io.open(v)
 for line in f:lines() do
  local et = line:match('"event_type":"(.-)"')
  if et then
   eT[et] = true
  end
 end
end
for k,v in pairs(eT) do
 io.write("- ")
 print(k)
end