How to use the rdf-ext.defaultRequest function in rdf-ext

function LdpStore (options) {
  options = options || {}

  this.parsers = options.parsers ? new rdf.Parsers(options.parsers) : rdf.parsers
  this.serializers = options.serializers ? new rdf.Serializers(options.serializers) : rdf.serializers
  this.defaultParser = options.defaultParser || 'text/turtle'
  this.defaultSerializer = options.defaultSerializer || 'text/turtle'
  this.defaultPatchSerializer = options.defaultPatchSerializer || options.defaultSerializer || 'text/turtle'
  this.request = options.request || rdf.defaultRequest
}