public boolean isAssignableFrom(Class<?> sourceType, Class<?> targetType) {
            return getKey().isAssignableFrom(sourceType) && getValue().isAssignableFrom(targetType);
        }
Source and target conversion type pair.
aws-java-sdk-dynamodb/src/main/java/com/amazonaws/services/dynamodbv2/datamodeling/DynamoDBTypeConverterFactory.java