'Arguments:
transformers ([BlockStructureTransformer]) - List of transformers
to add to the collection.
usage_info (any negotiated type) - A usage-specific object
that is passed to the block_structure and forwarded to all
requested Transformers in order to apply a
usage-specific transform. For example, an instance of
usage_info would contain a user object for which the
transform should be applied.
Raises:
TransformerException - if any transformer is not registered in the
Transformer Registry.'

def __init__(self, transformers=None, usage_info=None):

    self.usage_info = usage_info
    self._transformers = {'supports_filter': [], 'no_filter': []}
    if transformers:
        self.__iadd__(transformers)
