code: def add_network(self, network, netmask, area=0):
          
          if network == '' or netmask == '':
              raise ValueError('network and mask values '
                               'may not be empty')
          cmd = 'network {}/{} area {}'.format(network, netmask, area)
          return self.configure_ospf(cmd)
docs: Adds a network to be advertised by OSPF
  
             Args:
                 network (str):  The network to be advertised in dotted decimal
                                 notation
                 netmask (str):  The netmask to configure
                 area (str):  The area the network belongs to.
                              By default this value is 0
             Returns:
                 bool: True if the command completes successfully
             Exception:
                 ValueError: This will get raised if network or netmask
                             are not passed to the method