appendix classes nextwe extend the book class by defining the classwhich is used to represent single within book it adds two additional attributes to the three already defined by the book class and the two defined by the publication class class book )def __init__selfcodetitleauthorpublisheryear pages )super(__init__codetitleauthorpublisheryear self _self _pages pages def getbibentryself return super(getbibentry('str(self pp pages self _publisher 'self _year againthe constructor of the child class must call the parent' constructor with the use of the super(function this timethe five fields needed by the book class are passed as arguments to the constructor the two new fields defined by the child class are then created and initialized with the values from the appropriate arguments partial implementation of the remaining bibliography entry classes are defined below in similar fashion to those defined earlier class articlepublication )def __init__selfcodetitleauthorjournalvolumenumberyear )super(__init__codetitleauthor self _journal journal self _volume volume self _number number self _year year def getbibentryself class webpagepublication )def __init__selfcodetitleauthorurlmodified )super(__init__codetitleauthor self _url url self _modified modified def getbibentryself )