write an SVD section to a file handle

        Parameters
        ----------
        f : file handle

def write(self,f):
        """ write an SVD section to a file handle

        Parameters
        ----------
        f : file handle

        """
        f.write("* singular value decomposition\n")
        f.write(IFMT(self.svdmode)+'\n')
        f.write(IFMT(self.maxsing)+' '+FFMT(self.eigthresh)+"\n")
        f.write('{0}\n'.format(self.eigwrite))