Rule blocked: SEND-105.1 (CORERULES-557)

**Links to related JIRA Tickets**
- https://jira.cdisc.org/browse/CORERULES-557

**Rule Information**
- **Standard**: SENDIG
- **Rule ID**: 105-1
- **Rule Description**: If species is not included in DM it must be included in TS or TX.

**Describe the bug**
The rule as implemented in YAML works fine as long as both TS and TX are present. Especially for TX, this will however not always be the case.
So I tried to add YAML code that tests on the presence of TS and TX datasets (using "exists"), but I do get errors (zip file with all in- and output is attached).
My suspicion is that the rule engine thinks that "exists" (or "does_not_exist") is about a variable, rather than about a dataset in the whole submission, as the scope of the rule is DM (Sensitivity: Dataset).
Currently, the "exists" and "does_not_exist" operator is both used for variable presence checking as for dataset presence presence.
Maybe one could also add more explicit versions of the operator, e.g. "variable_exists" and "dataset_exists" (and their corresponding "does_not_exist" ones to be able to combine both variable as dataset presence in a single rule.