code: def emit(self, span_datas):
          
          project = 'projects/{}'.format(self.project_id)
  
          # Map each span data to it's corresponding trace id
          trace_span_map = defaultdict(list)
          for sd in span_datas:
              trace_span_map[sd.context.trace_id] += [sd]
  
          stackdriver_spans = []
          # Write spans to Stackdriver
          for _, sds in trace_span_map.items():
              # convert to the legacy trace json for easier refactoring
              # TODO: refactor this to use the span data directly
              trace = span_data.format_legacy_trace_json(sds)
              stackdriver_spans.extend(self.translate_to_stackdriver(trace))
  
          self.client.batch_write_spans(project, {'spans': stackdriver_spans})
docs: :type span_datas: list of :class:
              `~opencensus.trace.span_data.SpanData`
          :param list of opencensus.trace.span_data.SpanData span_datas:
              SpanData tuples to emit