code: public synchronized boolean logOut() {
          if (!isLoggedIn()) {
              return false;
          }
  
          mAuthenticationResult.clear();
          mAuthenticationResult = null;
  
          EvernoteUtil.removeAllCookies(getApplicationContext());
          return true;
      }
docs: Clears all stored session information. If the user is not logged in, then this is a no-op.
  
  @return {@code true} if the user successfully logged out, {@code false} if the user wasn't
  logged in.
  @see #isLoggedIn()