/** \mainpage SDF API Reference This documentation provides useful information about the Simulation Description Format API. The code reference is divided into the groups below. Should you find problems with this documentation - typos, unclear phrases, or insufficient detail - please create a new GitHub issue. Include sufficient detail to quickly locate the problematic documentation, and set the issue's fields accordingly: Assignee - blank; Kind - bug; Priority - minor; Version - blank.

Class
  List - Index of all classes in Gazebo, organized alphabetically
  Hierarchy - Index of classes, organized hierarchically according to their inheritance

Links
  Website: The main SDF website.
  Specification: Documentation of sdformat elements.
  Tutorials: Tutorials that describe how to use SDF.
  Download: How to download and install SDF

*/