Print the number of significant results using various metrics.

def get_num_sig(self, alpha=0.05):
        """Print the number of significant results using various metrics."""
        # Get the number of significant GO terms
        ctr = cx.Counter()
        flds = set(['FDR', 'Bonferroni', 'Benjamini', 'PValue'])
        for ntd in self.nts:
            for fld in flds:
                if getattr(ntd, fld) < alpha:
                    ctr[fld] += 1
        return ctr