code: public void reload(Environment environment) {
      Properties configuration = underlyingSource.getConfiguration(environment);
      cachedConfigurationPerEnvironment.put(environment.getName(), configuration);
    }
docs: Reload configuration set for a given {@code environment} from this source in a form of {@link Properties}.
  After reload completes the configuration can be accesses via {@link #getConfiguration(Environment)} method.
  
  @param environment environment to reload
  @throws MissingEnvironmentException when requested environment couldn't be found
  @throws IllegalStateException       when unable to fetch configuration