def METHOD_NAME(self, libraries):
    """Ensure that the list of libraries is valid.
    `library` is presumably provided as a command option 'libraries'.
    This method checks that it is a list of 2-tuples, where the tuples
    are (library_name, build_info_dict).
    Raise DistutilsSetupError if the structure is invalid anywhere;
    just returns otherwise.
    """
    if not isinstance(libraries, list):
        raise DistutilsSetupError(
              "'libraries' option must be a list of tuples")
    for lib in libraries:
        if not isinstance(lib, tuple) and len(lib) != 2:
            raise DistutilsSetupError(
                  "each element of 'libraries' must a 2-tuple")
        name, build_info = lib
        if not isinstance(name, str):
            raise DistutilsSetupError(
                  "first element of each tuple in 'libraries' "
                  "must be a string (the library name)")
        if '/' in name or (os.sep != '/' and os.sep in name):
            raise DistutilsSetupError("bad library name '%s': "
                   "may not contain directory separators" % lib[0])
        if not isinstance(build_info, dict):
            raise DistutilsSetupError(
                  "second element of each tuple in 'libraries' "
                  "must be a dictionary (build info)")