type: number
enum:
  # For fields with unknown cardinality.
  - 0 # CARDINALITY_UNKNOWN
  # For optional fields.
  - 1 # CARDINALITY_OPTIONAL
  # For required fields. Proto2 syntax only.
  - 2 # CARDINALITY_REQUIRED
  # For repeated fields.
  - 3 # CARDINALITY_REPEATED