code: func (c *Client) GetUsage(i *GetUsageInput) (*UsageResponse, error) {
  	r, err := c.Get("/stats/usage", &RequestOptions{
  		Params: map[string]string{
  			"from":   i.From,
  			"to":     i.To,
  			"by":     i.By,
  			"region": i.Region,
  		},
  	})
  	if err != nil {
  		return nil, err
  	}
  	var sr *UsageResponse
  	if err := decodeJSON(&sr, r.Body); err != nil {
  		return nil, err
  	}
  
  	return sr, nil
  }
docs: // GetUsage returns usage information aggregated across all Fastly services and grouped by region.