public String getKey() {
        return this.key;
    }
<p>
A unique identifier for the tag. Valid characters include Unicode letters, digits, white space, _, ., /, =, +, -,
%, and @.
</p>

@return A unique identifier for the tag. Valid characters include Unicode letters, digits, white space, _, ., /,
        =, +, -, %, and @.
aws-java-sdk-machinelearning/src/main/java/com/amazonaws/services/machinelearning/model/Tag.java