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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def register(self, plugin, name=None):
 """ Register a plugin and return its canonical name or None if the name is blocked from registering. Raise a ValueError if the plugin is already registered. """

        plugin_name = name or self.get_canonical_name(plugin)

        if plugin_name in self._name2plugin or plugin in self._plugin2hookcallers:
            if self._name2plugin.get(plugin_name, -1) is None:
                return  # blocked plugin, return None to indicate no registration
            raise ValueError(
                "Plugin already registered: %s=%s\n%s"
                % (plugin_name, plugin, self._name2plugin)
            )

        # XXX if an error happens we should make sure no state has been
        # changed at point of return
        self._name2plugin[plugin_name] = plugin

        # register matching hook implementations of the plugin
        self._plugin2hookcallers[plugin] = hookcallers = []
        for name in dir(plugin):
            hookimpl_opts = self.parse_hookimpl_opts(plugin, name)
            if hookimpl_opts is not None:
                normalize_hookimpl_opts(hookimpl_opts)
                method = getattr(plugin, name)
                hookimpl = HookImpl(plugin, plugin_name, method, hookimpl_opts)
                hook = getattr(self.hook, name, None)
                if hook is None:
                    hook = _HookCaller(name, self._hookexec)
                    setattr(self.hook, name, hook)
                elif hook.has_spec():
                    self._verify_hook(hook, hookimpl)
                    hook._maybe_apply_history(hookimpl)
                hook._add_hookimpl(hookimpl)
                hookcallers.append(hook)
        return plugin_name