code: @GET
      @Path("/relationshipdef/guid/{guid}")
      @Produces(Servlets.JSON_MEDIA_TYPE)
      public AtlasRelationshipDef getRelationshipDefByGuid(@PathParam("guid") String guid) throws AtlasBaseException {
          AtlasRelationshipDef ret = typeDefStore.getRelationshipDefByGuid(guid);
  
          return ret;
      }
docs: Get the relationship definition for the given guid
  @param guid relationship guid
  @return relationship definition
  @throws AtlasBaseException
  @HTTP 200 On successful lookup of the the relationship definition by it's guid
  @HTTP 404 On Failed lookup for the given guid