add dependency to total compute field

ex:

api.dependency('your sla filed from line',....etc fields)

def _amount_total()

Hi, 
you want to calculate the Total of the time that affects only sla. 
Considering that : 
your O2M field is :  timesheet_ids

the total field is : total_duration

the affects SLA :  sla

the Duration : duration

then : 

add (compute='_compute_total_duration', store=True) to total_duration

and 

@api.multi
@api.depends('timesheet_ids', 'timesheet_ids.sla', 'timesheet_ids.duration')
def _compute_total_duration(self):
    for record in self:
        total = False
        // Filter only on record with sla = Yes
        timesheets = record.timesheet_ids.filtered(lambda rec: rec.sla == 'yes')
        if timesheets:
            for timesheet in timesheets:
                total += timesheet.duration     // here, you may want to check how to add durations based on your field's signature
        record.total_duration = total