code: public Object getAttribute(String key) {
  		Object result;
  		if (attributes == null) {
  			result = null;
  		} else {
  			result = attributes.get(key);
  		}
  		return result;
  	}
docs: Gets an attribute attached to a call. Attributes are arbitrary contextual
  objects attached to a call.
  
  @param key
  attribute key/name
  @return attached attribute or null if there is none