docs: function getPrivate(instance) {
  
  	var map = weak_properties.get(instance);
  
  	if (!map) {
  		map = {
  			// Attribute configurations
  			attributes  : {},
  
  			// Attribute values for use in property getters
  			prop_values : {},
  
  			// Attribute string values
  			values      : {},
  
  			// New values that are beign set
  			new_values  : {}
  		};
  
  		weak_properties.set(instance, map);
  	}
  
  	return map;
  }