code: public Observable<RoleAssignmentInner> createByIdAsync(String roleId, RoleAssignmentCreateParameters parameters) {
          return createByIdWithServiceResponseAsync(roleId, parameters).map(new Func1<ServiceResponse<RoleAssignmentInner>, RoleAssignmentInner>() {
              @Override
              public RoleAssignmentInner call(ServiceResponse<RoleAssignmentInner> response) {
                  return response.body();
              }
          });
      }
docs: Creates a role assignment by ID.
  
  @param roleId The ID of the role assignment to create.
  @param parameters Parameters for the role assignment.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the RoleAssignmentInner object