def METHOD_NAME():
    hd = HourAndMinutesTimestamp(hour_str="09:00")
    expr = hd.filter_timestamp_column(
        EventsCallsTable.datetime, cmp_op=greater_or_equal
    )
    expected = "to_char(events.calls.datetime, 'HH24:MI') >= '09:00'"
    assert expected == get_string_representation(expr)
    hd = HourAndMinutesTimestamp(hour_str="12:40")
    expr = hd.filter_timestamp_column(EventsCallsTable.datetime, cmp_op=less_than)
    expected = "to_char(events.calls.datetime, 'HH24:MI') < '12:40'"
    assert expected == get_string_representation(expr)
    hd = HourAndMinutesTimestamp(hour_str=None)
    expr = hd.filter_timestamp_column(EventsCallsTable.datetime, cmp_op=less_than)
    expected = "true"
    assert expected == get_string_representation(expr)