<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def display_cached_string(self, bi):
 """ Logs the original builder messages, given the SConfBuildInfo instance bi. """

        if not isinstance(bi, SConfBuildInfo):
            SCons.Warnings.warn(SConfWarning,
              "The stored build information has an unexpected class: %s" % bi.__class__)
        else:
            self.display("The original builder output was:\n" +
                         ("  |" + str(bi.string)).replace("\n", "\n  |"))