code: function(name, value) {
        var prop = this.getFirstProperty(name);
  
        if (prop) {
          prop.setValue(value);
        } else {
          prop = this.addPropertyWithValue(name, value);
        }
  
        return prop;
      }
docs: Helper method that will update or create a property of the given name
  and sets its value. If multiple properties with the given name exist,
  only the first is updated.
  
  @param {String}               name         Property name to update
  @param {String|Number|Object} value        Property value
  @return {ICAL.Property}                    The created property