Updates a field with the provided attributes.
		Args:
			key	reqiured identifier for the pipeline or box
			field			StreakField object
			kwargs			{name, type} see StreakField for details
			return			(status code, field dict)

def _update_field(self, uri, field):
		'''Updates a field with the provided attributes.
		Args:
			key	reqiured identifier for the pipeline or box
			field			StreakField object
			kwargs			{name, type} see StreakField for details
			return			(status code, field dict)
		'''
		#req sanity check
		payload = None
		if  type(field) is not StreakField:
			return requests.codes.bad_request, None

		payload = field.to_dict(rw = True)
	
		#print(new_pl.attributes)
		#print(new_pl.to_dict())
		#raw_input()
		try:
			uri = '/'.join([
							uri, 
							field.attributes['key']
							])
		except KeyError:
			return requests.codes.bad_request, None
	
		code, data = self._req('post', uri , json.dumps(payload))
		
		return code, data