docs: function(attrs) {
      if (!attrs.ssl || includes(['NONE', 'UNVALIDATED', 'IFAVAILABLE', 'SYSTEMCA'], attrs.ssl)) {
        return;
      }
      if (attrs.ssl === 'SERVER' && !attrs.ssl_ca) {
        throw new TypeError('ssl_ca is required when ssl is SERVER.');
      } else if (attrs.ssl === 'ALL') {
        if (!attrs.ssl_ca) {
          throw new TypeError('ssl_ca is required when ssl is ALL.');
        }
  
        if (!attrs.ssl_private_key) {
          throw new TypeError('ssl_private_key is required when ssl is ALL.');
        }
  
        if (!attrs.ssl_certificate) {
          throw new TypeError('ssl_certificate is required when ssl is ALL.');
        }
      }
    }