Dimension const dim = dimension(*pi.base.bv);
Dimension const & dim0 = cell(0).dimension(*pi.base.bv);
Dimension const & dim1 = cell(1).dimension(*pi.base.bv);
Dimension const dim = dimension(*pi.base.bv);
Dimension const & dim0 = cell(0).dimension(*pi.base.bv);
Dimension const & dim1 = cell(1).dimension(*pi.base.bv);