Support catchall nodes
diff --git a/pkg/ast/ast.go b/pkg/ast/ast.go
index 1bc8bb4..7159393 100644
--- a/pkg/ast/ast.go
+++ b/pkg/ast/ast.go
@@ -1,5 +1,7 @@
 package ast
 
+// ast is the abstract syntax tree for the term mapper.
+
 import (
 	"encoding/json"
 )