stratify: how to stratify duplicated data?

[AppleXiao1995]

d3.stratify() cannot parse csv file with duplicated data.
However, I want to represent a structure like this:

my csv file looks like this:

id
a,
a.b,
a.b

When I use stratify(), it returns "duplicate: a.b". How can I achieve it?

[AppleXiao1995]

Thank you for your reply! However, I mean not only the leaf situation. In a situation like this:

csv:

id
a,
a.b,
a.b.c,
a.b,
a.b.d

The code cannot work and the error is "ambiguous".