Save the environment of a sv file to be used with soniv visualiser
        
        Args:
          outfname(str): full path to the file storing the environment

def save(self, outfname):
        """
        Save the environment of a sv file to be used with soniv visualiser
        
        Args:
          outfname(str): full path to the file storing the environment
        """
        f = BZ2File(outfname, 'w')
        self.doc.writexml(f, addindent='  ', newl='\n')
        f.close()