'Initialization for builder handler.
Args:
builder: Instance of Builder class.
Raises:
ListenerConfigurationError when builder is not a Builder class.'

def __init__(self, builder):

    if (not isinstance(builder, Builder)):
        raise yaml_errors.ListenerConfigurationError('Must    provide    builder    of    type    yaml_listener.Builder')
    self._builder = builder
    self._stack = None
    self._top = None
    self._results = []
