code: function getMailingsByTypes($types, $fields = array(), $page_index = 1, $page_size = 100)
      {
          $queryParameters = array(
              'page_index' => $page_index,
              'page_size' => $page_size,
              'order' => "DESC"
          );
  
          $queryParameters = $this->appendArrayFields($queryParameters, "types", $types);
          $queryParameters = $this->appendArrayFields($queryParameters, "fields", $fields);
  
          return $this->get('mailings/filter/types', $queryParameters);
      }
docs: Types can be selected from 'doi','trigger', 'trigger_template' or 'regular' <br />
  <br />
  @see MailingFields
  
  @param string[] $types
  This is the list of types to filter for
  @param string[] fields (default = empty)
  This list contains the fields that shall be returned with the result. If this list is empty, only the IDs will be returned. Valid fields are: state, type, name, and scheduleTime
  @param number page_index (default = 1)
  The index of the result page. The index must be greater or equal to 1.
  @param number page_size (default = 100)
  The maximum count of items in the result page. If provided, the value of page_size must be in the range 1 to 1000.
  @return
  @throws MaileonException