<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def reverse_search_history(event):
 """ Search backward starting at the current line and moving `up` through the history as necessary. This is an incremental search. """

    event.cli.current_search_state.direction = IncrementalSearchDirection.BACKWARD
    event.cli.push_focus(SEARCH_BUFFER)