Thank you for your response. Based on your comments, I was able to accomplish what I wanted to do. FYI, I am attaching the code.
# Creating the content to write in the command
mat_list = []
for i in range(1, 100):
mat_list.append("mat{}".format(i))
# Creating the command and writing the contents
for num in range(1, 100):
treeBody = Model.Geometry.Children[0].Children[num-1]
cs = treeBody.AddCommandSnippet()
cs.AppendText(mat_list[num-1])