+=item C<get_chart %params>
+
+Retrieves and returns a chart object valid for the given type
+C<$params{type}> and tax zone C<$params{taxzone}>
+(C<$params{taxzone_id}> is also recognized). The type must be one of
+the three key words C<income>, C<expense> and C<inventory>.
+
+This function uses the part's associated buchungsgruppe and uses the
+fields belonging to the tax zone given by C<$params{taxzone}> (range
+0..3).
+
+The information retrieved by the function is cached.
+