from enum google.protobuf.FieldDescriptorProto.Label
0 is reserved for errors
from enum value: LABEL_OPTIONAL = 1;
from enum value: LABEL_REPEATED = 3;
The required label is only allowed in google.protobuf. In proto3 and Editions it's explicitly prohibited. In Editions, the field_presence feature can be used to get this behavior.
field_presence
from enum value: LABEL_REQUIRED = 2;
Generated
from enum google.protobuf.FieldDescriptorProto.Label