code: public DynamoDBDeleteExpression withExpectedEntry(String attributeName, ExpectedAttributeValue expected) {
          if (expectedAttributes == null) {
              expectedAttributes = new HashMap<String,ExpectedAttributeValue>();
          }
          expectedAttributes.put(attributeName, expected);
          return this;
      }
docs: Adds one entry to the expected conditions and returns a pointer to this
  object for method-chaining.
  
  @param attributeName
  The name of the attribute.
  @param expected
  The expected attribute value.