code: func (c *Client) ExportField(field *Field) (io.Reader, error) {
  	span := c.tracer.StartSpan("Client.ExportField")
  	defer span.Finish()
  
  	var shardsMax map[string]uint64
  	var err error
  
  	status, err := c.Status()
  	if err != nil {
  		return nil, err
  	}
  	shardsMax, err = c.shardsMax()
  	if err != nil {
  		return nil, err
  	}
  	status.indexMaxShard = shardsMax
  	shardURIs, err := c.statusToNodeShardsForIndex(status, field.index.Name())
  	if err != nil {
  		return nil, err
  	}
  
  	return newExportReader(c, shardURIs, field), nil
  }
docs: // ExportField exports columns for a field.