def get json_path, json=nil
      if json.nil?
        json = JSON.parse body
      end
      results = JsonPath.new(json_path).on(json)
      if results.empty?
        raise %/Expected json path '#{json_path}' not found\n#{to_json_s}/
      end
      results.first
    end
def get json_path, json=nil
      if json.nil?
        json = JSON.parse body
      end
      results = JsonPath.new(json_path).on(json)
      if results.empty?
        raise %/Expected json path '#{json_path}' not found\n#{to_json_s}/
      end
      results.first
    end
Retrieve value of the first JSON element with given JSON path
 @param json_path [String] a valid JSON path expression
 @param json [String] optional JSON from which to apply JSON path, default to response body
 @return [Object] value of first retrieved JSON element in form of Ruby object
 @raise [Exception] if JSON path is invalid or no matching JSON element found