Wrong formula in "dimension_modularforms"

[David-Berghaus]

The formula of "dimension_modularforms" in

psage/psage/modform/arithgroup/mysubgroup.py

Line 2630 in 816bb6c

dim=self.dimension_cuspforms(k)+self._ncusps

is not correct.
Instead, it should be:
dim_modularforms(k) = dim_cuspforms(k) + ncusps - kronecker_delta(k,2)
Source: Theorem 5.6.18 in "Modular Forms - A classical approach" by Cohen and Strömberg.

For which examples do the dimension formulas offered by sage fail? Maybe we should simply use these which would also solve #32