#NEWLINE# def __getitem__( self , key ) : #NEWLINE# #INDENT# 'Lookup a variable or raise `KeyError` if the variable is\n        undefined.\n        ' #NEWLINE# item = self . resolve ( key ) #NEWLINE# if isinstance ( item , Undefined ) : #NEWLINE# #INDENT# raise KeyError ( item ) #NEWLINE# #UNINDENT# return item