Write summary of level and depth counts for active GO Terms.

def _write_summary_cnts(self, cnts):
        """Write summary of level and depth counts for active GO Terms."""
        # Count level(shortest path to root) and depth(longest path to root)
        # values for all unique GO Terms.
        max_val = max(max(dep for dep in cnts['depth']),
                      max(lev for lev in cnts['level']))
        self.log.write('Dep <-Depth Counts->  <-Level Counts->\n')
        self.log.write('Lev   BP    MF    CC    BP    MF    CC\n')
        self.log.write('--- ----  ----  ----  ----  ----  ----\n')
        for i in range(max_val+1):
            vals = ['{:>5}'.format(cnts[desc][i][ns]) for desc in sorted(cnts) for ns in self.nss]
            self.log.write('{:>02} {}\n'.format(i, ' '.join(vals)))