'Adds the given transformers to the collection.
Args:
transformers ([BlockStructureTransformer]) - List of transformers
to add to the collection.
Raises:
TransformerException - if any transformer is not registered in the
Transformer Registry.'

def __iadd__(self, transformers):

    unregistered_transformers = TransformerRegistry.find_unregistered(transformers)
    if unregistered_transformers:
        raise TransformerException('The    following    requested    transformers    are    not    registered:    {}'.format(unregistered_transformers))
    for transformer in transformers:
        if isinstance(transformer, FilteringTransformerMixin):
            self._transformers['supports_filter'].append(transformer)
        else:
            self._transformers['no_filter'].append(transformer)
    return self
