code: def _load_all_site_scons_dirs(topdir, verbose=None):
      
      platform = SCons.Platform.platform_default()
  
      def homedir(d):
          return os.path.expanduser('~/'+d)
  
      if platform == 'win32' or platform == 'cygwin':
          # Note we use $ here instead of %...% because older
          # pythons (prior to 2.6?) didn't expand %...% on Windows.
          # This set of dirs should work on XP, Vista, 7 and later.
          sysdirs=[
              os.path.expandvars('$ALLUSERSPROFILE\\Application Data\\scons'),
              os.path.expandvars('$USERPROFILE\\Local Settings\\Application Data\\scons')]
          appdatadir = os.path.expandvars('$APPDATA\\scons')
          if appdatadir not in sysdirs:
              sysdirs.append(appdatadir)
          sysdirs.append(homedir('.scons'))
  
      elif platform == 'darwin':  # MacOS X
          sysdirs=['/Library/Application Support/SCons',
                   '/opt/local/share/scons', # (for MacPorts)
                   '/sw/share/scons', # (for Fink)
                    homedir('Library/Application Support/SCons'),
                    homedir('.scons')]
      elif platform == 'sunos':   # Solaris
          sysdirs=['/opt/sfw/scons',
                   '/usr/share/scons',
                   homedir('.scons')]
      else:                       # Linux, HPUX, etc.
          # assume posix-like, i.e. platform == 'posix'
          sysdirs=['/usr/share/scons',
                   homedir('.scons')]
  
      dirs=sysdirs + [topdir]
      for d in dirs:
          if verbose:    # this is used by unit tests.
              print("Loading site dir ", d)
          _load_site_scons_dir(d)
docs: Load all of the predefined site_scons dir.
      Order is significant; we load them in order from most generic
      (machine-wide) to most specific (topdir).
      The verbose argument is only for testing.