def summary_table(params, proteins):
    """
    Returns a string representing a simple summary table of
    protein classifcations.
    """
    out = ''
    counts = {}
    for seqid in proteins:
        category = proteins[seqid]['category']
        if category not in counts:
            counts[category] = 1
        else:
            counts[category] += 1
    out += '\n\n# Number of proteins in each class:\n'
    pse_total = 0
    for c in counts:
        if 'PSE-' in c:
            pse_total += counts[c]
    counts['PSE(total)'] = pse_total
    for c in sorted(counts):
        if 'PSE-' in c:
            spacer = '  '
            pse_total += counts[c]
        else:
            spacer = ''
        out += '# %s%-15s\t%i\n' % (spacer, c, counts[c])
    return out
