Invoked by TLV class .toString method.
If the field is optional and unset, this is not invoked.
If the field is repeatable, this is invoked once per element.
TLV-VALUE, or Encoder.OmitEmpty to omit the field.
Remarks
Invoked by TLV class .encodeTo method.
If the field is optional and unset, this is not invoked.
If the field is repeatable, this is invoked once per element.
StructBuilder field type.