'Sets kwds[parameter] to value.
If kwds[parameter] exists and is not value, raises ConfigurationError.
Args:
kwds: The parameter dict, which maps parameter names (strings) to values.
parameter: The name of the parameter to set.
value: The value to set it to.'

def _require_parameter(self, kwds, parameter, value):

    if ((parameter in kwds) and (kwds[parameter] != value)):
        raise ConfigurationError(('%s    must    be    %s.' % (parameter, value)))
    kwds[parameter] = value
