@Override
    boolean atomic() {
        return true;
    }
Represents a <a href=
"http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.SpecifyingConditions.html#ConditionExpressionReference"
>Function</a> condition in building condition expression.
<p>
Underlying grammar:

<pre>
function ::=
   attribute_exists (path)
 | attribute_not_exists (path)
 | begins_with (path, operand)
 | contains (path, operand)
</pre>
<p>
This object is as immutable (or unmodifiable) as the underlying operand.
aws-java-sdk-dynamodb/src/main/java/com/amazonaws/services/dynamodbv2/xspec/FunctionCondition.java