get_imsi
Description:
Gets the International Mobile Subscriber Identity (IMSI) of the Sim object.
Warning: 
      
        
    
    The returned value is only valid until the property changes so it is only safe to use this function on the thread where this was constructed. Use dup_imsi if on another thread.
Parameters:
| this | A Sim. | 
Returns:
| The IMSI of the Sim object, or  |