code: public static String getKeyAnnotationValue(Method method) {
          C10NKey c10NKey = method.getAnnotation(C10NKey.class);
          if (null != c10NKey) {
              return c10NKey.value();
          }
          return null;
      }
docs: <p>Get the value provided with the {@link com.github.rodionmoiseev.c10n.C10NKey} annotation. If annotation
  is not declared returns <code>null</code>
  
  @param method method for which to retrieve the value {@link com.github.rodionmoiseev.c10n.C10NKey} annotation
  @return value of the declared annotation. <code>null</code> if not present.