statsFrom(input) {
    if (typeof input === "string") return this.countFromString(input);

    // What is going on here?
    // https://github.com/openai/openai-cookbook/blob/main/examples/How_to_count_tokens_with_tiktoken.ipynb Item 6.
    // The only option is to estimate. From repeated testing using the static values in the code we are always 2 off,
    // which means as of Nov 1, 2023 the additional factor on ln: 476 changed from 3 to 5.
    if (Array.isArray(input)) {
      const perMessageFactorTokens = input.length * 3;
      const tokensFromContent = input.reduce(
        (a, b) => a + this.countFromString(b.content),
        0
      );
      const diffCoefficient = 5;
      return perMessageFactorTokens + tokensFromContent + diffCoefficient;
    }

    throw new Error("Not a supported tokenized format.");
  }
Estimates the number of tokens in a string or array of strings.
@param {string | string[]} input
@returns {number}