code: def _create_virtual_network(self, region, resource_group_name, vnet_name):
          
          vnet_config = {
              'location': region,
              'address_space': {
                  'address_prefixes': ['10.0.0.0/27']
              }
          }
  
          try:
              vnet_setup = self.network.virtual_networks.create_or_update(
                  resource_group_name, vnet_name, vnet_config
              )
          except Exception as error:
              raise AzureCloudException(
                  'Unable to create vnet: {0}.'.format(error)
              )
  
          vnet_setup.wait()
docs: Create a vnet in the given resource group with default address space.