<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _robust_column_name(base_name, column_names):
 """ Generate a new column name that is guaranteed not to conflict with an existing set of column names. Parameters base_name : str The base of the new column name. Usually this does not conflict with the existing column names, in which case this function simply returns `base_name`. column_names : list[str] List of existing column names. Returns ------- robust_name : str The new column name. If `base_name` isn't in `column_names`, then `robust_name` is the same as `base_name`. If there are conflicts, a numeric suffix is added to `base_name` until it no longer conflicts with the column names. """

    robust_name = base_name
    i = 1

    while robust_name in column_names:
        robust_name = base_name + '.{}'.format(i)
        i += 1

    return robust_name