code: public static Predicate<HandlerInput> sessionAttribute(String key, Object value) {
          return i -> i.getRequestEnvelope().getSession() != null
                  && i.getAttributesManager().getSessionAttributes().containsKey(key)
                  && value.equals(i.getAttributesManager().getSessionAttributes().get(key));
      }
docs: Returns a predicate that returns to true if session attributes are included with the {@link HandlerInput}
  and contain the expected attribute value.
  @param key key of the attribute to evaluate
  @param value value of the attribute to evaluate
  @return true if session attributes are included with the {@link HandlerInput} and contain the expected
  attribute value.