code: def check_int(self, param, error_msg):
          
          if type(param) == int:
              return int(param)
          else:
              raise ValueError(error_msg)
docs: This function check if the parameter is int.
          If yes, the function returns the parameter,
          if not, it raises error message.
          
          **Args:**
          
          * `param` : parameter to check (int or similar)
  
          * `error_ms` : lowest allowed value (int), or None        
          
          **Returns:**
          
          * `param` : parameter (int)