title: Find most frequent group of 3 words in a sentence
body: <p>Suppose I have a text like</p>
  
  <pre><code>text="I came from the moon. He went to the other room. She went to the drawing room."
  </code></pre>
  
  <p>Most Frequent group of 3 words here is  <code>"went to the"</code></p>
  
  <p>I know how to find most frequent <code>bigram</code> or <code>trigram</code> but I am stuck in this.I want to find this solution <code>without using NLTK library</code>.</p>