Method outer

src/danfojs-base/transformers/merge.ts:290–297

* Generate outer key from leftKeyDict and rightKeyDict * The Key pass into basic method is the union of * leftKeyDict and rightKeyDict * @param leftKeyDict * @param rightKeyDict

(leftKeyDict: keyComb, rightKeyDict: keyComb)

   * @param rightKeyDict 
   */
  private outer(leftKeyDict: keyComb, rightKeyDict: keyComb): ArrayType2D {
    const keys = Object.keys(leftKeyDict)
    keys.push(...Object.keys(rightKeyDict))

    const UniqueKeys = Array.from(new Set(keys))
    const data = this.basic(UniqueKeys, leftKeyDict, rightKeyDict)
    return data
  }

  /**
   * Generate Key for basic method,