Firewalld ICMP types

Where does firewalld map it's ICMP types located in /usr/lib/firewalld/icmptypes to actual ICMP types like these: https://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml. For example, I don't see anything in echo-request.xml indicating it's ICMP type 8, so how does the firewall know when filtering ICMP packets? Thanks, Scott