This code works
import mlreportgen.report.*
import mlreportgen.dom.*
D = Template('NewTemplateName','docx','TemplateFromWhichWeAreAddingPart')
open(D)
dp = DocumentPart(D,'DocumenPartName');
append(D,dp)
close(D)
R = Report('Report','docx','NewTemplateName')
open(R)
append(R, TableOfContents)
close(R)
rptview(R)