code: func AttributeNotExists(nameBuilder NameBuilder) ConditionBuilder {
  	return ConditionBuilder{
  		operandList: []OperandBuilder{nameBuilder},
  		mode:        attrNotExistsCond,
  	}
  }
docs: // AttributeNotExists returns a ConditionBuilder representing the result of
  // the attribute_not_exists function in DynamoDB Condition Expressions. The
  // resulting ConditionBuilder can be used as a part of other Condition
  // Expressions or as an argument to the WithCondition() method for the Builder
  // struct.
  //
  // Example:
  //
  //     // condition represents the boolean condition of whether the item
  //     // attribute "Age" exists or not
  //     condition := expression.AttributeNotExists(expression.Name("Age"))
  //
  //     // Used in another Condition Expression
  //     anotherCondition := expression.Not(condition)
  //     // Used to make an Builder
  //     builder := expression.NewBuilder().WithCondition(condition)
  //
  // Expression Equivalent:
  //
  //     expression.AttributeNotExists(expression.Name("Age"))
  //     "attribute_not_exists (Age))"