Function parse 

pub fn parse<'a, C, L>(
    language: &L,
    diagnostics: &mut TemplateDiagnostics,
    template_text: &str,
    aliases_map: &TemplateAliasesMap,
) -> TemplateParseResult<TemplateRenderer<'a, C>>
where
    C: Clone + 'a,
    L: TemplateLanguage<'a> + ?Sized,
    L::Property: WrapTemplateProperty<'a, C>,

Parses text, expands aliases, then builds template evaluation tree.