def _flatten(self, field, items, transform = None):
		"""
		Extracts the entry `field` from each item in the supplied iterable, flattening any nested lists
		"""
		
		# Retrieve the value for each item in the iterable
		values = [item[field] for item in items]
		
		# Flatten any nested lists
		flattened = []
		for value in values:
			flattened.extend([value] if isinstance(value, str) else value)
		
		# Apply any supplied transformation function
		return transform(flattened) if transform != None else flattened
Extracts the entry `field` from each item in the supplied iterable, flattening any nested lists