code: def smart_str(s, encoding='utf-8', errors='strict'):
      
      if not isinstance(s, basestring):
          try:
              return str(s)
          except UnicodeEncodeError:
              if isinstance(s, Exception):
                  # An Exception subclass containing non-ASCII data that doesn't
                  # know how to print itself properly. We shouldn't raise a
                  # further exception.
                  return ' '.join([smart_str(arg, encoding, errors) for arg in s])
              return unicode(s).encode(encoding, errors)
      elif isinstance(s, unicode):
          return s.encode(encoding, errors)
      elif s and encoding != 'utf-8':
          return s.decode('utf-8', errors).encode(encoding, errors)
      else:
          return s
docs: Returns a bytestring version of 's', encoded as specified in 'encoding'.
  
      If strings_only is True, don't convert (some) non-string-like objects.
  
      from django