code: public Resource resolveConfigLocation() {
  		if (this.config == null) {
  			return null;
  		}
  		Assert.isTrue(this.config.exists(), () -> "Hazelcast configuration does not "
  				+ "exist '" + this.config.getDescription() + "'");
  		return this.config;
  	}
docs: Resolve the config location if set.
  @return the location or {@code null} if it is not set
  @throws IllegalArgumentException if the config attribute is set to an unknown
  location