Tweak example text (aws#144)

* Tweak example text

* Fix errant tab

Author: juneb

examples/src/data_key_caching_basic.py

@@ -10,7 +10,7 @@
 # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
 # ANY KIND, either express or implied. See the License for the specific
 # language governing permissions and limitations under the License.
-"""Example showing basic configuration and use of data key caching."""
+"""Example of encryption with data key caching."""
 import aws_encryption_sdk
 
 
@@ -28,13 +28,13 @@ def encrypt_with_caching(kms_cmk_arn, max_age_in_cache, cache_capacity):
     #   Max messages (or max bytes per) data key are optional
     MAX_ENTRY_MESSAGES = 100
 
-    # Create an encryption context.
+    # Create an encryption context
     encryption_context = {"purpose": "test"}
 
-    # Create a master key provider for the KMS master key
+    # Create a master key provider for the KMS customer master key (CMK)
     key_provider = aws_encryption_sdk.KMSMasterKeyProvider(key_ids=[kms_cmk_arn])
 
-    # Create a cache
+    # Create a local cache
     cache = aws_encryption_sdk.LocalCryptoMaterialsCache(cache_capacity)
 
     # Create a caching CMM
@@ -45,8 +45,9 @@ def encrypt_with_caching(kms_cmk_arn, max_age_in_cache, cache_capacity):
         max_messages_encrypted=MAX_ENTRY_MESSAGES,
     )
 
-    # When the call to encryptData specifies a caching CMM,
-    # the encryption operation uses the data key cache
+    # When the call to encrypt data specifies a caching CMM,
+    # the encryption operation uses the data key cache specified
+    # in the caching CMM
     encrypted_message, _header = aws_encryption_sdk.encrypt(
         source=my_data, materials_manager=caching_cmm, encryption_context=encryption_context
     )