code: public function offsetSet($offset, $value)
      {
          self::ensurePropertyType($value);
  
          if (is_null($offset)) {
              $this->data[] = $value;
          } else {
              $this->data[$offset] = $value;
          }
      }
docs: Sets a value for the given offset.
  
  @param mixed $offset The array index or null to add the value to the end of the array.
  @param mixed $value The value to add.
  
  @throws \DTS\eBaySDK\Exceptions\InvalidPropertyTypeException If the value is the wrong type for the array.