'Class initializer, this exposes configuration model to XBlock.
Arguments:
configuration_model (ConfigurationModel): configurations for an XBlock
Raises:
exception (ValueError): when configuration_model is not a subclass of
ConfigurationModel.'

def __init__(self, configuration_model):

    if (not (inspect.isclass(configuration_model) and issubclass(configuration_model, ConfigurationModel))):
        raise ValueError('Expected    ConfigurationModel    got    {0}    of    type    {1}'.format(configuration_model, type(configuration_model)))
    self.configuration = configuration_model
