code: function addVocabAsProperties(schema, terms_array) {
    if (!schema.properties) schema.properties = {};
    var propertySchema = schema.propertySchema || {};
    _.each(terms_array, function(term) {
      schema.properties[term] = vocab(term)
      if (propertySchema) {
        if (propertySchema.known) {
          propertySchema.known.push(term);
        }
        if (propertySchema.enum) {
          propertySchema.enum.push(term);
        }
      }
    });
  }
docs: addVocab adds a set of vocab terms as valid properties on a schema. Updates propertySchema if it's a simple single enumSchema