code: def find_implementations(sort_by=None):
      
      impls = [_describe_impl(t) for t in _list_impls()]
      if sort_by:
          impls.sort(key=attrgetter(sort_by))
      return tuple(impls)
docs: Returns a tuple of :class:`~escpos.helpers.Implementation` objects
      containing metadata for all known implementations (subclasses of
      :class:`~escpos.impl.epson.GenericESCPOS`) with vendor and model names, the
      implementation type and its fully qualified name.
  
      This example will print all vendor and model names, sorted by vendor name:
  
      .. sourcecode::
  
          for impl in find_implementations(sort_by='model.vendor'):
              print impl.model.vendor, ':', impl.model.name
  
      :param str sort_by: Attribute name to sort the resulting list (optional).
  
      :rtype: tuple