<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def list_(ctx, search_string, reverse, backend, used, inactive):
 """ List configured aliases. Aliases in red belong to inactive projects and trying to push entries to these aliases will probably result in an error. """

    if not reverse:
        list_aliases(ctx, search_string, backend, used, inactive=inactive)
    else:
        show_mapping(ctx, search_string, backend)