Fix error on @id: @nest

Author: rubensworks

lib/ContextParser.ts

@@ -421,7 +421,7 @@ Tried mapping ${key} to ${JSON.stringify(keyValue)}`, ERROR_CODES.INVALID_KEYWOR
             switch (objectKey) {
             case '@id':
               if (Util.isValidKeyword(objectValue)
-                && objectValue !== '@type' && objectValue !== '@id' && objectValue !== '@graph') {
+                && objectValue !== '@type' && objectValue !== '@id' && objectValue !== '@graph' && objectValue !== '@nest') {
                 throw new ErrorCoded(`Illegal keyword alias in term value, found: '${key}': '${JSON.stringify(value)}'`,
                   ERROR_CODES.INVALID_IRI_MAPPING);
               }

test/ContextParser-test.ts

@@ -1058,6 +1058,11 @@ Tried mapping @id to {}`, ERROR_CODES.KEYWORD_REDEFINITION));
           .not.toThrow();
       });
 
+      it('should not error on term with @id: @nest', async () => {
+        expect(() => parser.validate(<any> { term: { '@id': '@nest' } }, parseDefaults))
+          .not.toThrow();
+      });
+
       it('should error on term with @type: array', async () => {
         expect(() => parser.validate(<any> { term: { '@id': '@id', '@type': ['ex:a', 'ex:b'] } }, parseDefaults))
           .toThrow(new ErrorCoded(`The value of an '@type' must be a string, got '"object"'`,