@type t() :: %ExtFit.Record.FitDefinition{
  __chunk__: ExtFit.Chunk.t(),
  dev_field_defs: [ExtFit.Types.DevField.t()],
  endian: :little | :big,
  field_defs: [ExtFit.Types.Field.t()],
  global_mesg_num: nil | non_neg_integer(),
  is_developer_data: boolean(),
  local_mesg_num: non_neg_integer(),
  mesg_type: nil | map(),
  time_offset: non_neg_integer()
}