src/main/java/io/reactivex/internal/functions/ObjectHelper.java
public static <T> T requireNonNull(T object, String message) {
        if (object == null) {
            throw new NullPointerException(message);
        }
        return object;
    }
public static <T> T requireNonNull(T object, String message) {
        if (object == null) {
            throw new NullPointerException(message);
        }
        return object;
    }
Verifies if the object is not null and returns it or throws a NullPointerException
with the given message.
@param <T> the value type
@param object the object to verify
@param message the message to use with the NullPointerException
@return the object itself
@throws NullPointerException if object is null