Logging Fails When the Failure Results from an External Function

Is it possible to accommodate externally set (exported) bash functions?

I have several utilities defined as functions in my .bashrc.d files. If one of them fails, `logging.sh` returns:
```bash
hack/opt/bash-utils/util/logging.sh: line 49: pop_var_context: head of shell_variables not a function context
environment: line 37: pop_var_context: head of shell_variables not a function context
```