payment: Small fixes

- Semantic fixes bot.py (if XXX is not None: ...).
 - Documentation fixes (arguments which are optional).

telegram/bot.py

@@ -1843,21 +1843,21 @@ class Bot(TelegramObject):
             'prices': [p.to_dict() for p in prices]
         }
 
-        if photo_url:
+        if photo_url is not None:
             data['photo_url'] = photo_url
-        if photo_size:
+        if photo_size is not None:
             data['photo_size'] = photo_size
-        if photo_width:
+        if photo_width is not None:
             data['photo_width'] = photo_width
-        if photo_height:
+        if photo_height is not None:
             data['photo_height'] = photo_height
-        if need_name:
+        if need_name is not None:
             data['need_name'] = need_name
-        if need_phone_number:
+        if need_phone_number is not None:
             data['need_phone_number'] = need_phone_number
-        if need_shipping_address:
+        if need_shipping_address is not None:
             data['need_shipping_address'] = need_shipping_address
-        if is_flexible:
+        if is_flexible is not None:
             data['is_flexible'] = is_flexible
 
         return url, data
@@ -1877,12 +1877,12 @@ class Bot(TelegramObject):
             ok (bool): Specify True if delivery to the specified address is possible and False if
                 there are any problems (for example, if delivery to the specified address
                 is not possible)
-            shipping_options (List[:class:`telegram.ShippingOption`]): Required if ok is True. A
+            shipping_options (Optional[List[:class:`telegram.ShippingOption`]]): Required if ok is
-                list of available shipping options.
+                True. A list of available shipping options.
-            error_message (str): Required if ok is False. Error message in human readable form
+            error_message (Optional[str]): Required if ok is False. Error message in human readable
-                that explains why it is impossible to complete the order (e.g. "Sorry, delivery
+                form that explains why it is impossible to complete the order (e.g. "Sorry,
-                to your desired address is unavailable'). Telegram will display this message
+                delivery to your desired address is unavailable'). Telegram will display this
-                to the user.
+                message to the user.
 
         Returns:
             bool: On success, `True` is returned.
@@ -1895,9 +1895,9 @@ class Bot(TelegramObject):
 
         data = {'shipping_query_id': shipping_query_id, 'ok': ok}
 
-        if shipping_options:
+        if shipping_options is not None:
             data['shipping_options'] = shipping_options
-        if error_message:
+        if error_message is not None:
             data['error_message'] = error_message
 
         return url, data
@@ -1912,11 +1912,11 @@ class Bot(TelegramObject):
             pre_checkout_query_id (str): Unique identifier for the query to be answered
             ok (bool): Specify True if everything is alright (goods are available, etc.) and the
                 bot is ready to proceed with the order. Use False if there are any problems.
-            error_message (str): Required if ok is False. Error message in human readable form that
+            error_message (Optional[str]): Required if ok is False. Error message in human readable
-                explains the reason for failure to proceed with the checkout (e.g. "Sorry, somebody
+                form that explains the reason for failure to proceed with the checkout (e.g.
-                just bought the last of our amazing black T-shirts while you were busy filling out
+                "Sorry, somebody just bought the last of our amazing black T-shirts while you were
-                your payment details. Please choose a different color or garment!"). Telegram will
+                busy filling out your payment details. Please choose a different color or
-                display this message to the user.
+                garment!"). Telegram will display this message to the user.
 
         Returns:
             bool: On success, `True` is returned.
@@ -1929,7 +1929,7 @@ class Bot(TelegramObject):
 
         data = {'pre_checkout_query_id': pre_checkout_query_id, 'ok': ok}
 
-        if error_message:
+        if error_message is not None:
             data['error_message'] = error_message
 
         return url, data