Fix for Merge Node Maps algorithm.

- Exclude `@type` from added values in Merge Node Maps step 2.2.1.
- Fix for w3c/json-ld-api#407.

Author: davidlehn

CHANGELOG.md

@@ -1,5 +1,8 @@
 # jsonld ChangeLog
 
+### Fixed
+- Exclude `@type` from added values in Merge Node Maps step 2.2.1.
+
 ## 3.0.0 - 2020-03-10
 
 ### Notes

lib/nodeMap.js

@@ -241,7 +241,7 @@ api.mergeNodeMapGraphs = graphs => {
       const mergedNode = merged[id];
 
       for(const property of Object.keys(node).sort()) {
-        if(isKeyword(property)) {
+        if(isKeyword(property) && property !== '@type') {
           // copy keywords
           mergedNode[property] = util.clone(node[property]);
         } else {