1 to 1 mapping between two columns

[Nandha95]

I'm trying to implement a check for validating that a pair of columns have a 1-1 relationship, that is, the values in column a should have only one value in column b.
The following dataframe is valid because each value of column a has the same value in column b even though the rows are repeated.

df = pd.DataFrame.from_records([
    {"a": 1, "b": 2, "c": 3},
    {"a": 1, "b": 2, "c": 3},
])

I tried to use the joint uniqueness parameter, but it checks at a row level. I also tried implementing a dataframelevel check which does work, however, it does not tell me how many rows have failed. Is there a way to get this implemented?

[Nandha95]

I see that a similar question was raised in #978, so I'll take that as a reference.