hello guys, i want to make field2 invisible until i get value in field1 how to do this i already attrs but it says odoo17 onwards attrs & states not working please help me and one more thing i have two button start and stop, i want to make stop button invisible when start button is not in active state and when start is activated i want to make start button invisible after activated . 

for field :

xml code :  <field name="estimate_time"/>

                            <field name="re_estimated_time"  modifiers="{'invisible': [('estimate_time', '=', False)]}"/>

python code:  estimate_time = fields.Char(string="Estimated Time (Hours)",)

    re_estimated_time = fields.Char(string="Re-Estimated Time")

for button:

python:    time_start = fields.Datetime(string='Start Time')

    time_end = fields.Datetime(string='End Time')

xml : <button name="action_start_time" type="object" string="Start Time" class="btn-primary"

                            invisible="time_start != 'False'"/>

                    <button name="action_stop_time" type="object" string="Stop Time" class="btn-secondary"/>