def METHOD_NAME(self, env, dependent_spec):
    """Set TCLLIBPATH to include the tcl-shipped directory for
    extensions and any other tcl extension it depends on.
    For further info see:
    * https://wiki.tcl-lang.org/page/TCLLIBPATH
    """
    for d in dependent_spec.traverse(deptype=('build', 'run', 'test')):
        if d.package.extends(self.spec):
            # Tcl libraries may be installed in lib or lib64, see #19546
            for lib in ['lib', 'lib64']:
                tcllibpath = join_path(d.prefix, lib)
                if os.path.exists(tcllibpath):
                    env.prepend_path('TCLLIBPATH', tcllibpath, separator=' ')