public SamplingRuleUpdate addAttributesEntry(String key, String value) {
        if (null == this.attributes) {
            this.attributes = new java.util.HashMap<String, String>();
        }
        if (this.attributes.containsKey(key))
            throw new IllegalArgumentException("Duplicated keys (" + key.toString() + ") are provided.");
        this.attributes.put(key, value);
        return this;
    }
Add a single Attributes entry

@see SamplingRuleUpdate#withAttributes
@returns a reference to this object so that method calls can be chained together.
aws-java-sdk-xray/src/main/java/com/amazonaws/services/xray/model/SamplingRuleUpdate.java