Make PYSON more Pythonic

work.py

@@ -5,7 +5,7 @@ from collections import deque, defaultdict
 from heapq import heappop, heappush
 from trytond.model import ModelView, ModelSQL, fields
 from trytond.wizard import Wizard
-from trytond.pyson import Eval, Not, Equal
+from trytond.pyson import Eval
 from trytond.transaction import Transaction
 from trytond.pool import Pool
 
@@ -34,8 +34,8 @@ class Work(ModelSQL, ModelView):
     leveling_delay = fields.Float("Leveling Delay")
     back_leveling_delay = fields.Float("Leveling Delay")
     allocations = fields.One2Many('project.allocation', 'work', 'Allocations',
-            states={
-                'invisible': Not(Equal(Eval('type'), 'task')),
+        states={
+            'invisible': Eval('type') != 'task',
             }, depends=['type'])
     duration = fields.Function(fields.Float('Duration'), 'get_function_fields')
     early_start_time = fields.DateTime("Early Start Time", readonly=True)