code: def return_env(self, exists=True):
          
          env = dict(
              include=self._build_paths('include',
                                        [self.VCIncludes,
                                         self.OSIncludes,
                                         self.UCRTIncludes,
                                         self.NetFxSDKIncludes],
                                        exists),
              lib=self._build_paths('lib',
                                    [self.VCLibraries,
                                     self.OSLibraries,
                                     self.FxTools,
                                     self.UCRTLibraries,
                                     self.NetFxSDKLibraries],
                                    exists),
              libpath=self._build_paths('libpath',
                                        [self.VCLibraries,
                                         self.FxTools,
                                         self.VCStoreRefs,
                                         self.OSLibpath],
                                        exists),
              path=self._build_paths('path',
                                     [self.VCTools,
                                      self.VSTools,
                                      self.VsTDb,
                                      self.SdkTools,
                                      self.SdkSetup,
                                      self.FxTools,
                                      self.MSBuild,
                                      self.HTMLHelpWorkshop,
                                      self.FSharp],
                                     exists),
          )
          if self.vc_ver >= 14 and os.path.isfile(self.VCRuntimeRedist):
              env['py_vcruntime_redist'] = self.VCRuntimeRedist
          return env
docs: Return environment dict.
  
          Parameters
          ----------
          exists: bool
              It True, only return existing paths.