Specs

t() :: %Spandex.SpanContext{
  baggage: Keyword.t(),
  parent_id: Spandex.id(),
  priority: integer(),
  trace_id: Spandex.id()
}

From the OpenTracing specification:

Each SpanContext encapsulates the following state:

• Any OpenTracing-implementation-dependent state (for example, trace and span ids) needed to refer to a distinct Span across a process boundary
• Baggage Items, which are just key:value pairs that cross process boundaries