generator that yields channel groups as pandas DataFrames. If there
        are multiple occurences for the same channel name inside a channel
        group, then a counter will be used to make the names unique
        (<original_name>_<counter>)

def iter_groups(self):
        """ generator that yields channel groups as pandas DataFrames. If there
        are multiple occurences for the same channel name inside a channel
        group, then a counter will be used to make the names unique
        (<original_name>_<counter>)

        """

        for i, _ in enumerate(self.groups):
            yield self.get_group(i)