diff --git a/__init__.py b/__init__.py
index dffcbb0..ecd11fa 100644
--- a/__init__.py
+++ b/__init__.py
@@ -1,6 +1,6 @@
-#This file is part margin module for Tryton.
-#The COPYRIGHT file at the top level of this repository contains
-#the full copyright notices and license terms.
+# This file is part margin module for Tryton.
+# The COPYRIGHT file at the top level of this repository contains the full
+# copyright notices and license terms.
 from trytond.pool import Pool
 from . import configuration
 from . import sale
diff --git a/configuration.py b/configuration.py
index 5eb30b5..631e523 100644
--- a/configuration.py
+++ b/configuration.py
@@ -2,9 +2,7 @@
 # The COPYRIGHT file at the top level of this repository contains
 # the full copyright notices and license terms.
 from trytond.model import fields
-from trytond.pool import Pool
-from trytond.pyson import Eval, Bool
-from trytond.pool import PoolMeta
+from trytond.pool import Pool, PoolMeta
 
 __all__ = ['Configuration', 'ConfigurationSaleMethod']
 
@@ -29,7 +27,8 @@ class Configuration:
 
     @classmethod
     def default_sale_margin_method(cls, **pattern):
-        return cls.multivalue_model('sale_margin_method').default_sale_margin_method()
+        return cls.multivalue_model(
+            'sale_margin_method').default_sale_margin_method()
 
 
 class ConfigurationSaleMethod:
diff --git a/sale.py b/sale.py
index 9264b95..1f46b4a 100644
--- a/sale.py
+++ b/sale.py
@@ -17,8 +17,8 @@ class Sale:
     margin = fields.Function(fields.Numeric('Margin',
             digits=(16, Eval('currency_digits', 2),),
             depends=['currency_digits'],
-            help='It gives profitability by calculating the difference '
-                'between the Unit Price and Cost Price.'),
+            help=('It gives profitability by calculating the difference '
+                'between the Unit Price and Cost Price.')),
         'get_margin')
     margin_cache = fields.Numeric('Margin Cache',
         digits=(16, Eval('currency_digits', 2)),
@@ -184,7 +184,8 @@ class SaleLine:
                     if not price:
                         return Decimal('1.0')
                     else:
-                        return (self.margin / price).quantize(Decimal('0.0001'))
+                        return (
+                            self.margin / price).quantize(Decimal('0.0001'))
                 if line2.type == 'line':
                     if sale_margin_method == 'unit_price':
                         price += line2.get_margin_unit_price()
diff --git a/tests/__init__.py b/tests/__init__.py
index 6d94c85..dd1a12a 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -1,6 +1,6 @@
-#This file is part sale_margin module for Tryton.
-#The COPYRIGHT file at the top level of this repository contains
-#the full copyright notices and license terms.
+# This file is part sale_margin module for Tryton.
+# The COPYRIGHT file at the top level of this repository contains the full
+# copyright notices and license terms.
 
 try:
     from trytond.modules.sale_margin.tests.test_sale_margin import suite