def check_unique(dataframe, identifier_list):
    """
    Verifies that dataframe is uniquely identified by the variables in identifier_list
    :param dataframe: a pandas dataframe
    :param identifier_list: a list of variable names. Must be contained in either the index
    or the variables of dataframe
    :return: a dataframe of identifiers that are not uniquely identified along with the counts of
    how many times they occurred. If the dataframe is uniquely identified, the function returns
    an empty dataframe
    """
    unique_identifier = dataframe.groupby(by = identifier_list).count().iloc[:, 0]
    unique_identifier.name = 'Count'
    unique_identifier = unique_identifier[unique_identifier > 1]
    return unique_identifier.to_frame()