code: public function content($content, $contentType = self::CONTENT_TYPE_HTML, $charset = null)
      {
          if (isset($this->params) && is_array($this->params)) {
              $content = $this->setDynamicContent($this->params, $content);
          }
  
          $this->getMessage()->setBody($content, $contentType, $charset);
  
          return $this;
      }
docs: Set the body of this message, either as a string, or as an instance of
  {@link \Swift_OutputByteStream}.
  
  @param mixed $content
  @param string $contentType optional
  @param string $charset     optional
  
  @return $this
  
  @see \Swift_Message::setBody()