code: public final Session getSession(SessionName name) {
  
      GetSessionRequest request =
          GetSessionRequest.newBuilder().setName(name == null ? null : name.toString()).build();
      return getSession(request);
    }
docs: Gets a session. Returns `NOT_FOUND` if the session does not exist. This is mainly useful for
  determining whether a session is still alive.
  
  <p>Sample code:
  
  <pre><code>
  try (SpannerClient spannerClient = SpannerClient.create()) {
  SessionName name = SessionName.of("[PROJECT]", "[INSTANCE]", "[DATABASE]", "[SESSION]");
  Session response = spannerClient.getSession(name);
  }
  </code></pre>
  
  @param name Required. The name of the session to retrieve.
  @throws com.google.api.gax.rpc.ApiException if the remote call fails