Example for eles.umerge() is malformed in the docs #1996

- Fixes formatting.
- Clarifies on what collections these functions should be used.

documentation/md/collection/merge.md

@@ -2,17 +2,22 @@
 
 <span class="important-indicator"></span> This function modifies the calling collection instead of returning a new one.  Use of this function should be considered for performance in some cases, but otherwise should be avoided.  Consider using `eles.union()` instead.
 
+<span class="important-indicator"></span> Use this function only on new collections that you create yourself, using `cy.collection()`.  This ensures that you do not unintentionally modify another collection.
+
 ## Examples
 
 With a collection:
 ```js
+var col = cy.collection(); // new, empty collection
 var j = cy.$('#j');
 var e = cy.$('#e');
 
-j.merge(e);
+col.merge( j ).merge( e );
 ```
 
 With a selector:
 ```js
-cy.$('#j').merge('#e');
-```
+var col = cy.collection(); // new, empty collection
+
+col.merge('#j').merge('#e');
+```

documentation/md/collection/unmerge.md

@@ -2,16 +2,27 @@
 
 <span class="important-indicator"></span> This function modifies the calling collection instead of returning a new one.  Use of this function should be considered for performance in some cases, but otherwise should be avoided.  Consider using `eles.filter()` or `eles.remove()` instead.
 
+<span class="important-indicator"></span> Use this function only on new collections that you create yourself, using `cy.collection()`.  This ensures that you do not unintentionally modify another collection.
+
 ## Examples
 
 With a collection:
+
 ```js
-var j = cy.nodes();
+var col = cy.collection(); // new, empty collection
 var e = cy.$('#e');
 
-j.unmerge(e);
+col.merge( cy.nodes() );
+
+col.unmerge( e );
 ```
 
 With a selector:
+
 ```js
-cy.nodes().unmerge('#e');
+var col = cy.collection(); // new, empty collection
+
+col.merge( cy.nodes() );
+
+col.unmerge('#e');
+```