def decay(self, mass_frac):
import nuutils as u<EOL>global decayed_multi_d<EOL>decayed_multi_d=[]<EOL>for iii in range(len(mass_frac)):<EOL><INDENT>jj=-<NUM_LIT:1><EOL>decayed=[]<EOL>for i in range(len(u.decay_raw)):<EOL><INDENT>if u.jdum[i] > <NUM_LIT:0.5>:<EOL><INDENT>jj=jj+<NUM_LIT:1><EOL>dummy=<NUM_LIT:0.><EOL>for j in range(len(u.decay_raw[i])):<EOL><INDENT>try:<EOL><INDENT>dum_str = u.decay_raw[i][j]<EOL>dummy = dummy + float(self.mass_frac[iii][u.cl[dum_str.lower().capitalize()]])<EOL><DEDENT>except KeyError:<EOL><INDENT>None<EOL><DEDENT>except IndexError:<EOL><INDENT>None<EOL><DEDENT><DEDENT>decayed.append(dummy)<EOL><DEDENT><DEDENT>decayed_multi_d.append(decayed)<EOL><DEDENT>
this module simply calculate abundances of isotopes after decay.

It requires that before it is used a call is made to
_read_iso_abund_marco and _stable_species.

Parameters
----------
mass_frac : list
    alist of mass_frac dicts.

See Also
--------
_read_iso_abund_marco(), nuutils.Utils._stable_species()