code: def ec2_subnet_subnet_id(self, lookup, default=None):
      
      subnets = EFAwsResolver.__CLIENTS["ec2"].describe_subnets(Filters=[{
        'Name': 'tag:Name',
        'Values': [lookup]
      }])
      if len(subnets["Subnets"]) > 0:
        return subnets["Subnets"][0]["SubnetId"]
      else:
        return default
docs: Return:
        the ID of a single subnet or default/None if no match
      Args:
        lookup: the friendly name of the subnet to look up (subnet-<env>-a or subnet-<env>-b)
        default: the optional value to return if lookup failed; returns None if not set