@type t() :: %Google.Api.Expr.V1alpha1.Constant{
__unknown_fields__: [
{field_number :: integer(), Protobuf.Wire.Types.wire_type(),
value :: term()}
],
constant_kind:
{:null_value, Google.Protobuf.NullValue.t()}
| {:bool_value, boolean()}
| {:int64_value, integer()}
| {:uint64_value, non_neg_integer()}
| {:double_value, float() | :infinity | :negative_infinity | :nan}
| {:string_value, String.t()}
| {:bytes_value, binary()}
| {:duration_value, Google.Protobuf.Duration.t() | nil}
| {:timestamp_value, Google.Protobuf.Timestamp.t() | nil}
| nil
}