@type structured_attributes() :: [{String.t(), String.t()}]

@type t() :: %VCF.Metadata{
  key: String.t(),
  line: pos_integer() | nil,
  raw: String.t() | nil,
  value: value()
}

@type value() ::
  VCF.Version.t()
  | VCF.FieldDefinition.t()
  | structured_attributes()
  | String.t()