bool containsFeature( string attrName, attrValue )
This method returns TRUE if the feature defined by the given arguments (See General Search Criteria) is contained within the map.
Note: this method operates on all features contained in the map, whether persistent or transient. However, because of its generality it is a less efficient way to search for transient features. Thus, if it is known at compile time that the feature to be queried is transient, the FeatureAPI method mapContainsFeature should be used.