<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def rename_channels(self, *, verbose=True, **kwargs):
 """Rename a set of channels. Parameters kwargs Keyword arguments of the form current:'new'. verbose : boolean (optional) Toggle talkback. Default is True """

        # ensure that items will remain unique
        changed = kwargs.keys()
        for k, v in kwargs.items():
            if v not in changed and v in self.keys():
                raise wt_exceptions.NameNotUniqueError(v)
        # compile references to items that are changing
        new = {}
        for k, v in kwargs.items():
            obj = self[k]
            index = self.channel_names.index(k)
            # rename
            new[v] = obj, index
            Group._instances.pop(obj.fullpath, None)
            obj.natural_name = str(v)
            # remove old references
            del self[k]
        # apply new references
        names = list(self.channel_names)
        for v, value in new.items():
            obj, index = value
            self[v] = obj
            names[index] = v
        self.channel_names = names
        # finish
        if verbose:
            print("{0} channel(s) renamed:".format(len(kwargs)))
            for k, v in kwargs.items():
                print("  {0} --> {1}".format(k, v))