code: def find_sdk_dir(self):
          
          if not SCons.Util.can_read_reg:
              debug('find_sdk_dir(): can not read registry')
              return None
  
          hkey = self.HKEY_FMT % self.hkey_data
          debug('find_sdk_dir(): checking registry:{}'.format(hkey))
  
          try:
              sdk_dir = common.read_reg(hkey)
          except SCons.Util.WinError as e:
              debug('find_sdk_dir(): no SDK registry key {}'.format(repr(hkey)))
              return None
  
          debug('find_sdk_dir(): Trying SDK Dir: {}'.format(sdk_dir))
  
          if not os.path.exists(sdk_dir):
              debug('find_sdk_dir():  {} not on file system'.format(sdk_dir))
              return None
  
          ftc = os.path.join(sdk_dir, self.sanity_check_file)
          if not os.path.exists(ftc):
              debug("find_sdk_dir(): sanity check {} not found".format(ftc))
              return None
  
          return sdk_dir
docs: Try to find the MS SDK from the registry.
  
          Return None if failed or the directory does not exist.