similarity(strA, strB, locale) {
    if (strA === strB) {
      return 1;
    }

    const [termFreqVecA, termFreqVecB] = this.getTermFreqVectors(
      strA,
      strB,
      locale
    );
    return this.cosineSimilarity(termFreqVecA, termFreqVecB);
  }
Calculates cosine-similarity from two sentences
@param {string} left Left string
@param {string} right Right string
@returns {number} cosine between two sentences representend in VSM