code: function getResponseHeader(sHeaderName) {
  		var sResponseHeader;
  
  		sHeaderName = sHeaderName.toLowerCase();
  
  		for (sResponseHeader in this.headers) {
  			if (sResponseHeader.toLowerCase() === sHeaderName) {
  				return this.headers[sResponseHeader];
  			}
  		}
  	}
docs: The getResponseHeader() method imitates the jqXHR.getResponseHeader() method for a $batch
  error response.
  
  @param {string} sHeaderName The header name
  @returns {string} The response header value