code: def _DetermineOperatingSystem(self, searcher):
      
      find_specs = [
          file_system_searcher.FindSpec(
              location='/etc', case_sensitive=False),
          file_system_searcher.FindSpec(
              location='/System/Library', case_sensitive=False),
          file_system_searcher.FindSpec(
              location='/Windows/System32', case_sensitive=False),
          file_system_searcher.FindSpec(
              location='/WINNT/System32', case_sensitive=False),
          file_system_searcher.FindSpec(
              location='/WINNT35/System32', case_sensitive=False),
          file_system_searcher.FindSpec(
              location='/WTSRV/System32', case_sensitive=False)]
  
      locations = []
      for path_spec in searcher.Find(find_specs=find_specs):
        relative_path = searcher.GetRelativePath(path_spec)
        if relative_path:
          locations.append(relative_path.lower())
  
      # We need to check for both forward and backward slashes since the path
      # spec will be OS dependent, as in running the tool on Windows will return
      # Windows paths (backward slash) vs. forward slash on *NIX systems.
      windows_locations = set([
          '/windows/system32', '\\windows\\system32', '/winnt/system32',
          '\\winnt\\system32', '/winnt35/system32', '\\winnt35\\system32',
          '\\wtsrv\\system32', '/wtsrv/system32'])
  
      operating_system = definitions.OPERATING_SYSTEM_FAMILY_UNKNOWN
      if windows_locations.intersection(set(locations)):
        operating_system = definitions.OPERATING_SYSTEM_FAMILY_WINDOWS_NT
  
      elif '/system/library' in locations:
        operating_system = definitions.OPERATING_SYSTEM_FAMILY_MACOS
  
      elif '/etc' in locations:
        operating_system = definitions.OPERATING_SYSTEM_FAMILY_LINUX
  
      return operating_system
docs: Tries to determine the underlying operating system.
  
      Args:
        searcher (dfvfs.FileSystemSearcher): file system searcher.
  
      Returns:
        str: operating system for example "Windows". This should be one of
            the values in definitions.OPERATING_SYSTEM_FAMILIES.