Error: rule defined twice

I'm trying to learn zeek signature
signature file name: dns.sig

signature dns-intel{
ip-proto == udp
dst-port == 53
payload /.*life|.*bar/
event "[Suspicious DNS Query]" }

Zeek file name: myfirst.zeek

event signature_match (state: signature_state, msg: string, data: string) {
  if (state$sig_id == "dns-intel") {
    print fmt ("[Suspicious DNS query] %s", state$conn$dns$query)

I'm getting error in line 5 : rule defined twice
what's the problem here ??

Can you provide a runnable example?