def start_span(operation_name, child_of: active_span, **args)
      span = @tracer.start_span(operation_name, child_of: child_of, **args)
      @managed_span_source.make_active(span)
    end
def start_span(operation_name, child_of: active_span, **args)
      span = @tracer.start_span(operation_name, child_of: child_of, **args)
      @managed_span_source.make_active(span)
    end
Starts a new active span.

 @param operation_name [String] The operation name for the Span

 @param child_of [SpanContext, Span] SpanContext that acts as a parent to
        the newly-started Span. If default argument is used then the currently
        active span becomes an implicit parent of a newly-started span.

 @return [SpanManager::ManagedSpan] The newly-started active Span