code: public Number getNumberTag(String key) {
  		Object value = tags.get(key);
  		if (value instanceof Number) {
  			return (Number) value;
  		}
  		return null;
  	}
docs: This method returns the tag value, associated with the supplied key, if it exists and has a {@link Number} type.
  
  @param key The tag key
  @return The value, if exists and is a {@link Number} type, otherwise null