+=item C<call_sub $name, @args>
+
+Calls the sub C<$name> on C<$self> with the arguments C<@args> and
+returns its result. This is meant for situations in which the sub's
+name is a composite, e.g.
+
+ my $chart_id = $buchungsgruppe->call_sub(($is_sales ? "income" : "expense") . "_accno_id_${taxzone_id}");
+
+=item C<call_sub_if $name, $check, @args>
+
+Calls the sub C<$name> on C<$self> with the arguments C<@args> if
+C<$check> is trueish. If C<$check> is a code reference then it will be
+called with C<$self> as the only argument and its result determines
+whether or not C<$name> is called.
+
+Returns the sub's result if the check is positive and C<$self>
+otherwise.
+
+=item C<get_first_conflicting @attributes>
+
+Returns the first object for which all properties listed in
+C<@attributes> equal those in C<$self> but which is not C<$self>. Can
+be used to check whether or not an object's columns are unique before
+saving or during validation.
+
+=item C<load_cached @ids>
+
+Loads objects from the database which haven't been cached before and
+caches them for the duration of the current request (see
+L<SL::Request/cache>).
+
+This method can be called both as an instance method and a class
+method. It loads objects for the corresponding class (e.g. both
+C<SL::DB::Part-E<gt>load_cached(…)> and
+C<$some_part-E<gt>load_cached(…)> will load parts).
+
+Currently only classes with a single primary key column are supported.
+
+Returns the cached object for the first ID.
+
+=item C<invalidate_cached @ids>
+
+Deletes all cached instances of this class (see L</load_cached>) for
+the given IDs.
+
+If called as an instance method without further arguments then the
+object's ID is used.
+
+Returns the object/class it was called on.
+