help with variable modifiers

[budyhead]

does anybody know why these two modifier does not work? using them just simply return the entire abstract or nothing.

{article.get_abstract|substr:1:100}
{article.get_summary|100}


this is the documentation so why dont the two above work?

{* applying modifier to a variable *}
<vte:value select="{article.get_title|strtoupper}" />

{* using format_date to format the current date *}
<vte:value select="{article.created|format_date:'d/m/Y'}" />

{* counting the number of elements in a list *}
<vte:value select="{article_list|count}" />

{* using PHP built-in function as modifier for query parameter *}
<vtearam name="search_cid" value="{CURRENT_CATEGORY.get_id},{CURRENT_CATEGORY .get_descendent_ids|implode:','}" />

{* forcing number of characters for article abstract text *}
<vte:value select="{article.get_summary|NUMBER_OF_CHARACTERS} " />