    # File lib/fog/ibm/requests/compute/modify_key.rb, line 28
            def modify_key(key_name, params={})
              response = Excon::Response.new
              if key_exists? key_name
                if params['public_key']
                  self.data[:keys][key_name]['keyMaterial'] = public_key
                  self.data[:keys][key_name]['lastModifiedTime'] = Fog::IBM::Mock.launch_time
                end
                if params['default']
                  self.data[:keys].values.each do |key|
                    key['default'] = false
                  end
                  self.data[:keys][key_name]['default'] = true
                end
                response.status = 200
                response.body = {"success"=>true}
              else
                response.status = 404
              end
              response
            end