code: public static boolean isValidStringNotBlank(final GraphObject node, final PropertyKey<String> key, final ErrorBuffer errorBuffer) {
  
  		if (StringUtils.isNotBlank(node.getProperty(key))) {
  
  			return true;
  		}
  
  		errorBuffer.add(new EmptyPropertyToken(node.getType(), key));
  
  		return false;
  	}
docs: Checks whether the value for the given property key of the given node
  is a non-empty string.
  
  @param node the node
  @param key the property key
  @param errorBuffer the error buffer
  
  @return true if the condition is valid