ECalBackend Base class for calendar/tasks backend implementations. @backend: @Returns: @backend: @Returns: @backend: @Returns: @backend: @cal: @backend: @cal: @backend: @query: @backend: @Returns: @backend: @cal: @backend: @cal: @backend: @cal: @backend: @cal: @backend: @cal: @backend: @cal: @only_if_exists: @username: @password: @backend: @cal: @backend: @cal: @calobj: @backend: @cal: @calobj: @mod: @backend: @cal: @uid: @rid: @mod: @backend: @cal: @uid: @auid: @backend: @cal: @calobj: @backend: @cal: @calobj: @backend: @cal: @backend: @cal: @uid: @rid: @backend: @cal: @sexp: @backend: @cal: @uid: @rid: @backend: @Returns: @backend: @query: @backend: @Returns: @backend: @mode: @backend: @cal: @tzid: @backend: @cal: @object: @backend: @cal: @tzid: @backend: @cal: @tzobj: @backend: @cal: @change_id: @backend: @cal: @users: @start: @end: @backend: @Returns: @backend: @tzid: @Returns: @backend: @backend: @proxy: @backend: @calobj: @backend: @old_object: @object: @backend: @id: @old_object: @object: @backend: @status: @mode: @backend: @backend: @message: @backend: @status: @backend: @message: @percent: @backend: @read_only: @backend: @address: