'Creates a printable representation of the collection suitable
for reading by humans or parsing from scripts.  Actually scripts
would be better off reading the JSON in the collections files
directly.'

def to_string(self):

    values = self.listing.values()[:]
    values.sort()
    results = []
    for (i, v) in enumerate(values):
        results.append(v.to_string())
    if (len(values) > 0):
        return '\n\n'.join(results)
    else:
        return _('No    objects    found')
