ORB_SLAM之error: ‘Sim3’ in namespace ‘g2o’ does not name a type简单暴力解决问题

ORB_SLAM之error: ‘Sim3’ in namespace ‘g2o’ does not name a type

以下在ubuntu20.04下完成，在编译ORB_SLAM时经常出现以下类似错误，不要担心，也不要重新安装g2o类似的软件包，去找这个sim3所在的头文件，要是找不到就
把下面的放在文件前面就好啦！！！

#include <g2o/core/base_vertex.h>
#include <g2o/core/base_binary_edge.h>
#include <g2o/core/block_solver.h>
#include <g2o/core/optimization_algorithm_levenberg.h>
#include <g2o/solvers/eigen/linear_solver_eigen.h>
#include <g2o/types/slam3d/types_slam3d.h>
#include <g2o/types/slam3d/types_slam3d.h>
#include <g2o/core/sparse_optimizer.h>
#include <g2o/core/block_solver.h>
#include <g2o/core/factory.h>
#include <g2o/core/optimization_algorithm_factory.h>
#include <g2o/core/optimization_algorithm_gauss_newton.h>
#include <g2o/core/robust_kernel.h>
#include <g2o/core/robust_kernel_factory.h>
#include <g2o/core/optimization_algorithm_levenberg.h>
#include <g2o/solvers/eigen/linear_solver_eigen.h>
#include <g2o/solvers/csparse/linear_solver_csparse.h>