private static boolean hasTagAlready(Javadoc doc, JavadocTag tag) {
        requireNonNull(doc);
        requireNonNull(tag);
        
		return doc.getTags().stream().anyMatch(t -> 
			tag.getName().equals(t.getName())
			&& tag.getValue().equals(t.getValue())
		);
	}
Checks if the specified tag is already defined in the supplied
documentation block. 

@param doc  the documentation block
@param tag  the tag to check
@return     {@code true} if it exists, else {@code false}
common-parent/codegen/src/main/java/com/speedment/common/codegen/controller/AutoJavadoc.java