cif2pdb - rename in the fancy way only to A?

[mmagnus]

rh:~$ rna_pdb_tools.py --cif2pdb 4v6x.cif
Warning: some of the chains in this mmCIF file has chain names with more char than 1, e.g. AB, and the PDB format needs single-letter code, e.g. A.
rna chain A -> A # of atoms: 38377 4v6x_B2_nA_fCIF.pdb
rna chain B -> B # of atoms: 1604 4v6x_BC_nB_fCIF.pdb
rna chain C -> C # of atoms: 84946 4v6x_A5_nC_fCIF.pdb
rna chain D -> D # of atoms: 2578 4v6x_A7_nD_fCIF.pdb
rna chain E -> E # of atoms: 3334 4v6x_A8_nE_fCIF.pdb