[dist4]message_header  // num_bytes
[u4]0                  // version
[u4]0                  // interface ID
[u4]18                 // name
[u4]0                  // flags
[u4]0                  // padding
[anchr]message_header

[dist4]method18_params  // num_bytes
[u4]0                   // version
[u4]0                   // param0: Size 0 indicating the inlined union is null.
[u4]0                   // param0: Tag field ignored.
[u8]0                   // param0: Payload field ignored.
[anchr]method18_params