`module State : sig ... end`
`module Content : sig ... end`
`type t````=` `{`

`mutable state : State.t;`
`buf : Email_message__.Email_grammar.token Core.Queue.t;`

`}```
`val create : unit ‑> t`
`module Result : sig ... end`
`val combine : t ‑> Result.t ‑> unit`
`include Result.Std`
`val return : ?⁠new_state:State.t ‑> Email_message__.Email_grammar.token list ‑> Result.t`
`val return_eof : Result.t`
`val return_error : string ‑> Result.t`
`module Error : sig ... end`