I need to find the sum of cases in col2 where for each set in col1 (ABC), the col2 value has a Y in col3 100% of the time. In this case, B1 &
D1 meet this criteria, so N=2. Support in pandas or SQL are helpful (both are ideal). 

```
| col1 |  col2 |  col3 |  col4 |  col5 |
|------|-------|-------|-------|-------|
|  A   |   A1  |    N  |  1    |  256  |
|  A   |   B1  |    Y  |  2    |  3    |
|  A   |   C1  |    N  |  3    |  323  |
|  B   |   F1  |    N  |  1    |  89   |
|  B   |   B1  |    Y  |  2    |  256  |
|  C   |   D1  |    Y  |  1    |  3    |
|  D   |   A1  |    N  |  1    |  32   |
|  D   |   C1  |    Y  |  2    |  893  |

```