@classmethod
def tree_to_dict(cls, tree):
    """
        Given an OptionTree, convert it into the equivalent dictionary format.
        """
    specs = {}
    for k in tree.keys():
        spec_key = '.'.join(k)
        specs[spec_key] = {}
        for grp in tree[k].groups:
            kwargs = tree[k].groups[grp].kwargs
            if kwargs:
                specs[spec_key][grp] = kwargs
    return specs
