TAttributeCollection implements a collection for storing attribute names and values.
Besides all functionalities provided by {@link TMap}, TAttributeCollection
allows you to get and set attribute values like getting and setting
properties. For example, the following usages are all valid for a
TAttributeCollection object:
$collection->Text='text';
echo $collection->Text;
They are equivalent to the following:
$collection->add('Text','text');
echo $collection->itemAt('Text');
Note, attribute names are case-insensitive. They are converted to lower-case
in the collection storage.