attribute and slot usage in one schema

[djarecka]

I would like to use both slots and attributes in one schema. I was having issue with creating attributes column (see #128 ), but I found a cli option --use-attributes, but if I use this option it looks like everything is treated as attributes and I would like to have an option to do both.

For example, for a table:

| Proposed BICAN Field | SubGroup/LinkML Class Name | Range   |
|----------------------|----------------------------|---------|
|> slot                | class                      | range   |
|----------------------|----------------------------|---------|
| attr1                | class1                     | integer |
| attr2                | class2                     | float   |
| slot1                |                            | float   |
| slot1                | class1                     |         |

I would think that attr1 and attr2 could be treated as attributes but slot1 that has two rows (one with class the other without) could be treated as a slot