import re


def get_duplicates_of(df, name):
    """
    Return the names of columns that correspond to duplicates: X, X -> X, X.1

    :param df: pandas dataframe
    :param name: original name (eg. X for X.1)
    :return: list of strings
    """
    regex = re.compile(r'^(__name__(?:\.\d+)?)$'.replace('__name__', name))
    return [c for c in df.columns if bool(regex.match(c))]