What is the purpose of having an array as optional in protobuf?

edit

The purpose of having an array as optional in protobuf is to allow for optional fields that can contain multiple values. An optional array field allows for flexibility in the data structure, as it allows for a field to be included but not necessarily contain any values. Additionally, it allows for the possibility of having multiple values within a single field, enabling more complex data structures to be represented in a protobuf message.