'A Config object that has been bound to specific data.
@param config   The config that is bound - must handle get_value
@param bind_to  The data it is bound to - must support subscripting
@param grab_key The key in bind_to in which to expect this configuration
@param prefix   The prefix in the config tree leading to this configuration'

def __init__(self, config, bind_to, grab_key=_ANONYMOUS, prefix=''):

    self.config = config
    self.bind_to = bind_to
    self.grab_key = grab_key
    self.prefix = prefix
