Write a method to sort an array of strings so that all the anagrams are in the same group.

Note: This problem is slightly different from the original one the book.

Example:

Input: ["eat", "tea", "tan", "ate", "nat", "bat"],
Output:
[
  ["ate","eat","tea"],
  ["nat","tan"],
  ["bat"]
]

Notes:

• All inputs will be in lowercase.
• The order of your output does not matter.