Improve elasticsearch instrumentation examples

Author: andremm

instrumentation/opentelemetry-instrumentation-elasticsearch/src/opentelemetry/instrumentation/elasticsearch/__init__.py

@@ -32,7 +32,7 @@
 
     from opentelemetry.instrumentation.elasticsearch import ElasticsearchInstrumentor
     import elasticsearch
-
+    from datetime import datetime
 
     # instrument elasticsearch
     ElasticsearchInstrumentor().instrument()
@@ -49,6 +49,8 @@
 
 .. code-block:: python
 
+    from opentelemetry.instrumentation.elasticsearch import ElasticsearchInstrumentor
+
     ElasticsearchInstrumentor("my-custom-prefix").instrument()
 
 The instrument() method accepts the following keyword args:
@@ -67,6 +69,7 @@ def response_hook(span: Span, response: dict)
 
     from opentelemetry.instrumentation.elasticsearch import ElasticsearchInstrumentor
     import elasticsearch
+    from datetime import datetime
 
     def request_hook(span, method, url, kwargs):
         if span and span.is_recording():