params keys are Strings

guides/source/form_helpers.md

@@ -553,7 +553,7 @@ outputs (with actual option values omitted for brevity)
 which results in a `params` hash like
 
 ```ruby
-{:person => {'birth_date(1i)' => '2008', 'birth_date(2i)' => '11', 'birth_date(3i)' => '22'}}
+{'person' => {'birth_date(1i)' => '2008', 'birth_date(2i)' => '11', 'birth_date(3i)' => '22'}}
 ```
 
 When this is passed to `Person.new` (or `update`), Active Record spots that these parameters should all be used to construct the `birth_date` attribute and uses the suffixed information to determine in which order it should pass these parameters to functions such as `Date.civil`.
@@ -881,19 +881,19 @@ end
 
 ```ruby
 {
-    :person => {
-        :name => 'John Doe',
-        :addresses_attributes => {
-            '0' => {
-                :kind => 'Home',
-                :street => '221b Baker Street',
-            },
-            '1' => {
-                :kind => 'Office',
-                :street => '31 Spooner Street'
-            }
-        }
+  'person' => {
+    'name' => 'John Doe',
+    'addresses_attributes' => {
+      '0' => {
+        'kind' => 'Home',
+        'street' => '221b Baker Street'
+      },
+      '1' => {
+        'kind' => 'Office',
+        'street' => '31 Spooner Street'
+      }
     }
+  }
 }
 ```