Java Only Map
Java HashMap backed implementation of ReadableMap and WritableMap Instances of this class SHOULD NOT be used for communication between java and JS, use instances of WritableNativeMap created via Arguments#createMap or just ReadableMap interface if you want your "native" module method to take a map from JS as an argument.
Main purpose for this class is to be used in java-only unit tests, but could also be used outside of tests in the code that operates only in java and needs to communicate with RN modules via their JS-exposed API.