public static <T> T notNull(T object, Supplier<String> messageProvider) {
    checkArgument(object != null, messageProvider);
    return object;
  }
Assert that the supplied {@link Object} is not {@code null}.

@param object          the object to check
@param messageProvider violation message
@return the supplied object as a convenience
@throws IllegalArgumentException if the supplied object is {@code null}
spock-core/src/main/java/org/spockframework/util/Checks.java