takes a tuple of keys
		returns node found in cfg_dict
		found by traversing cfg_dict by successive 
		application of keys from element_path

def read_element_using_argtuple(self, argtuple):
		"""
		takes a tuple of keys
		returns node found in cfg_dict
		found by traversing cfg_dict by successive 
		application of keys from element_path
		"""

		# doesn't support DELIMITED, only dict-based formats
		if self.format == FMT_DELIMITED:
			return None

		node = self.cfg_dict
		for key in argtuple:
			node = node[key]
		return node