Odoo Server ErrorTraceback (most recent call last):
  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\http.py", line 643, in _handle_exception    return super(JsonRequest, self)._handle_exception(exception)  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\http.py", line 680, in dispatch    result = self._call_function(**self.params)  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\http.py", line 316, in _call_function    return checked_call(self.db, *args, **kwargs)  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\service\model.py", line 118, in wrapper    return f(dbname, *args, **kwargs)  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\http.py", line 309, in checked_call    result = self.endpoint(*a, **kw)  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\http.py", line 959, in __call__    return self.method(*args, **kw)  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\http.py", line 509, in response_wrap    response = f(*args, **kw)  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\addons\web\controllers\main.py", line 892, in call_kw    return self._call_kw(model, method, args, kwargs)  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\addons\web\controllers\main.py", line 884, in _call_kw    return getattr(request.registry.get(model), method)(request.cr, request.uid, *args, **kwargs)  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\api.py", line 250, in wrapper    return old_api(self, *args, **kwargs)  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\api.py", line 381, in old_api    result = method(recs, *args, **kwargs)  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\models.py", line 6034, in onchange    value = record[name]  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\models.py", line 5740, in __getitem__    return self._fields[key].__get__(self, type(self))  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\fields.py", line 831, in __get__    self.determine_draft_value(record)  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\fields.py", line 944, in determine_draft_value    self._compute_value(record)  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\odoo9\openerp\fields.py", line 880, in _compute_value    getattr(records, self.compute)()  File "C:\Users\isgm103.ISGM\Desktop\isgmnm\isgm_erp_extension\models\emp_overtime.py", line 183, in compute_amount   
 from_dt = datetime.datetime.strptime(self.working_time_in, DATETIME_FORMAT)
TypeError: strptime() argument 1 must be string, not bool
my code
'amount':fields.float('Amount',compute='compute_amount',store=True,readonly=True),
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@api.depends('overtime_duration', 'rate')    def compute_amount(self):
              wage = 0.0      
  rate = 1.0      
  total_var = 0.0               
print " working time in in compute_amount > " , self.working_time_in       
print " working time out in compute_amount > " , self.working_time_out              
  DATETIME_FORMAT = "%Y-%m-%d %H:%M:%S"      
  from_dt = datetime.datetime.strptime(self.working_time_in, DATETIME_FORMAT)      
  print "From_dt",from_dt       
to_dt = datetime.datetime.strptime( self.working_time_out, DATETIME_FORMAT)      
  print "To_dt",to_dt     
   timedelta = to_dt - from_dt       
print "time delta " , timedelta       
diff_min = timedelta.days + float(timedelta.seconds) / 60       
print "Diff_min",diff_min       
self.overtime_duration = diff_min       
print " compute_duration end .."               
for line in self:
 print " for... self line"         
   if self.overtime_id:
                wage = self.overtime_id.rate_per_min                              
  if self.rate == 'first':
                    rate = 1.0               
elif self.rate == 'second':
                    rate = 1.5                                
   self.amount = wage*self.overtime_duration*rate        
    total_var += self.amount           
print total_var
#        
self.overtime_id.total_amount = self.overtime_id.total_amount+self.amount
