Prevent ontoconvert from crashing when the --iri option is given (#902)

# Description
Prevent ontoconvert from crashing unintentionally when the --iri option
is given.

Include also some minor code cleanup.

## Type of change
<!-- Put an `x` in the box that applies. -->
- [ ] Bug fix.
- [ ] New feature.
- [ ] Documentation update.
- [ ] Test update.

## Checklist
<!-- Put an `x` in the boxes that apply. You can also fill these out
after creating the PR. -->

This checklist can be used as a help for the reviewer.

- [ ] Is the code easy to read and understand?
- [ ] Are comments for humans to read, not computers to disregard?
- [ ] Does a new feature has an accompanying new test (in the CI or unit
testing schemes)?
- [ ] Has the documentation been updated as necessary?
- [ ] Does this close the issue?
- [ ] Is the change limited to the issue?
- [ ] Are errors handled for all outcomes?
- [ ] Does the new feature provide new restrictions on dependencies, and
if so is this documented?

## Comments
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applicable. -->

Co-authored-by: Francesca L. Bleken <48128015+francescalb@users.noreply.github.com>

Author: jesper-friis

ontopy/utils.py

@@ -34,6 +34,8 @@
 if TYPE_CHECKING:
     from typing import Optional, Union
 
+    from ontopy import Ontology
+
 
 # Preferred language
 PREFERRED_LANGUAGE = "en"
@@ -860,14 +862,20 @@ def recur(o):
     return layout
 
 
-def copy_annotation(onto, src, dst):
+def copy_annotation(onto: "Ontology", src: str, dst: str):
     """In all classes and properties in `onto`, copy annotation `src` to `dst`.
 
     Arguments:
         onto: Ontology to work on.
         src: Name of source annotation.
         dst: Name or IRI of destination annotation.  Use IRI if the
             destination annotation is not already in the ontology.
+
+    Example:
+
+        copy_annotation(
+            onto, "elucidation", "http://www.w3.org/2000/01/rdf-schema#comment"
+        )
     """
     if onto.world[src]:
         src = onto.world[src]

tools/ontoconvert

@@ -191,7 +191,7 @@ def main(argv: list = None):
         action="store_true",
         help=(
             "Whether to annotate all entities with the base IRI of the source "
-            "ontology using `dcterms:source` relations.  This is contextual "
+            "ontology using `rdfs:isDefinedBy` relations.  This is contextual "
             "information that is otherwise lost when ontologies are inferred "
             "and/or squashed."
         ),
@@ -274,7 +274,7 @@ def main(argv: list = None):
         if args.iri:
             onto.iri = args.iri
 
-        if args.base_iri:
+        if args.base_iri and args.base_iri != onto.base_iri:
             onto.base_iri = args.base_iri
 
         if args.annotate_source: