fix typos and add missing docstrings

Author: wescpy

README.md

@@ -21,7 +21,7 @@ Codelabs begin with a "START" code base then walks developers through that migra
 
 ## Cost
 
-App Engine is not a free service. While you may not have needed to enable billing in App Engine's early days, [all applications now require an active billing account](https://cloud.google.com/appengine/docs/standard/payment-instrument) backed by a financial instrument (usually a credit card). Don't worry, App Engine (and other GCP products) still have an ["Always Free" tier](https://cloud.google.com/free/docs/gcp-free-tier#always-free), and as long as you stay within those limits, you won't incur billing. Also check the App Engine [pricing](https://cloud.google.com/appengine/pricing) and [quotas](https://cloud.google.com/appengine/code quotas) pages for more information.
+App Engine is not a free service. While you may not have needed to enable billing in App Engine's early days, [all applications now require an active billing account](https://cloud.google.com/appengine/docs/standard/payment-instrument) backed by a financial instrument (usually a credit card). Don't worry, App Engine (and other GCP products) still have an ["Always Free" tier](https://cloud.google.com/free/docs/gcp-free-tier#always-free), and as long as you stay within those limits, you won't incur billing. Also check the App Engine [pricing](https://cloud.google.com/appengine/pricing) and [quotas](https://cloud.google.com/appengine/quotas) pages for more information.
 
 
 ## Why

mod0-baseline/main.py

@@ -18,10 +18,12 @@
 from google.appengine.ext.webapp import template
 
 class Visit(ndb.Model):
+    'Visit entity registers visitor IP address & timestamp'
     visitor   = ndb.StringProperty()
     timestamp = ndb.DateTimeProperty(auto_now_add=True)
 
 def store_visit(remote_addr, user_agent):
+    'create new Visit entity in Datastore'
     Visit(visitor='{}: {}'.format(remote_addr, user_agent)).put()
 
 def fetch_visits(limit):

mod1-framework/main.py

@@ -18,6 +18,7 @@
 app = Flask(__name__)
 
 class Visit(ndb.Model):
+    'Visit entity registers visitor IP address & timestamp'
     visitor   = ndb.StringProperty()
     timestamp = ndb.DateTimeProperty(auto_now_add=True)
 

mod2a-cloudndb/main.py

@@ -19,6 +19,7 @@
 ds_client = ndb.Client()
 
 class Visit(ndb.Model):
+    'Visit entity registers visitor IP address & timestamp'
     visitor   = ndb.StringProperty()
     timestamp = ndb.DateTimeProperty(auto_now_add=True)
 

mod2b-cloudndb/main.py

@@ -19,6 +19,7 @@
 ds_client = ndb.Client()
 
 class Visit(ndb.Model):
+    'Visit entity registers visitor IP address & timestamp'
     visitor   = ndb.StringProperty()
     timestamp = ndb.DateTimeProperty(auto_now_add=True)
 

mod7-gaetasks/main.py

@@ -22,6 +22,7 @@
 app = Flask(__name__)
 
 class Visit(ndb.Model):
+    'Visit entity registers visitor IP address & timestamp'
     visitor   = ndb.StringProperty()
     timestamp = ndb.DateTimeProperty(auto_now_add=True)
 

mod8-cloudtasks/main.py

@@ -29,6 +29,7 @@
 QUEUE_PATH = ts_client.queue_path(PROJECT_ID, REGION_ID, QUEUE_NAME)
 
 class Visit(ndb.Model):
+    'Visit entity registers visitor IP address & timestamp'
     visitor   = ndb.StringProperty()
     timestamp = ndb.DateTimeProperty(auto_now_add=True)