I2C Gravity Multiplexer - Arduino

I am fairly new to Arduino world. I am trying to use multiple I2C Sensors on a Gravity I2C multiplexer. I see that the address has been set to 0x70. When i run the basic frame structure given by the company i never recognizes the multiplex.  

#include <DFRobot_I2C_Multiplexer.h>
#include <Wire.h>

//*Create an I2C Multiplexer object, the default address of I2C Multiplexer is 0X70*/

void setup(void){
 DFRobot_I2CMultiplexer I2CMulti (0x70);
I2CMulti.selectPort(0); //Select Port 0
... //Initialize the I2C Device on Port 0
I2CMulti.selectPort(1); //Select Port 1
... //Initialize the I2C Device on Port 1
.
.
.
I2CMulti.selectPort(8); //Select Port 8
... //Initialize the I2C Device on Port 8
}
void loop(void)
{
I2CMulti.selectPort(0); //Select Port 0
... //Communicate with the I2C Device on Port 0
I2CMulti.selectPort(1); //Select Port 1
... //Communicate with the I2C Device on Port 1
.
.
.
I2CMulti.selectPort(8); //Select Port 8
... //Communicate with the I2C Device on Port 8
}

The highlighted code gives me error stating  exit status 1
'DFRobot_I2CMultiplexer' does not name a type; did you mean 'DFRobot_I2C_Multiplexer'?