code: def format_decimal_field(__, prec, number, locale):
      
      prec = 0 if prec is None else int(prec)
      if number < 0:
          prec += 1
      return format(number, u'0%dd' % prec)
docs: Formats a decimal field:
  
      .. sourcecode::
  
         1234 ('D') -> 1234
         -1234 ('D6') -> -001234