Gets one/all field in a box
		Args:
			box_key 		key for pipeline
			field_key 			key for field (default: None i.e. ALL)
			returns				status code, field dict or list thereof

def get_box_field(self, box_key, field_key = None):
		'''Gets one/all field in a box
		Args:
			box_key 		key for pipeline
			field_key 			key for field (default: None i.e. ALL)
			returns				status code, field dict or list thereof
		'''
		#does not work
		self._raise_unimplemented_error()
		
		uri = '/'.join([self.api_uri,
						self.boxes_suffix,
						box_key,
						self.fields_suffix
						])
		if field_key:
			uri = '/'.join([uri, field_key])

		return self._req('get', uri)