Better deal with bad MRSs in conversion

There are two separate issues that are fixed here:

* When multiple non-quantifier EPs share an ARG0 it caused problems
  with mapping variables to quantifiers

* When the INDEX was not used by any EP it caused a lookup error

Fixes #267

CHANGELOG.md

@@ -15,6 +15,10 @@ these changes are prefixed with "**BREAKING**"
 * `delphin.codecs.edspenman` now properly reads predicate names
 * `delphin.codecs.edspenman` and `delphin.codecs.dmrspenman` now wrap
   `PenmanError` in `PyDelphinException` ([#266][])
+* `delphin.mrs.MRS.quantification_pairs()` detects and ignores when
+  quantifier(s) are shared by multiple EPs ([#267][])
+* `delphin.dmrs.from_mrs()` detects when an INDEX is specified but is
+  not the intrinsic argument of any EP ([#267][])
 
 ### Changed
 
@@ -1248,4 +1252,5 @@ information about changes, except for
 [#263]: https://github.com/delph-in/pydelphin/issues/263
 [#264]: https://github.com/delph-in/pydelphin/issues/264
 [#266]: https://github.com/delph-in/pydelphin/issues/266
+[#267]: https://github.com/delph-in/pydelphin/issues/267
 [#268]: https://github.com/delph-in/pydelphin/issues/268

delphin/dmrs/_operations.py

@@ -33,7 +33,11 @@ def from_mrs(m, representative_priority=None):
                  for ep in m.rels if not ep.is_quantifier()}
 
     top = _mrs_get_top(m.top, hcmap, reps, id_to_nid)
-    index = iv_to_nid[m.index] if m.index else None
+    # some bad MRSs have an INDEX that isn't the ARG0 of any EP, so
+    # make sure it exists first
+    index = None
+    if m.index and m.index in iv_to_nid:
+        index = iv_to_nid[m.index]
     nodes = _mrs_to_nodes(m, id_to_nid)
     links = _mrs_to_links(m, hcmap, reps, iv_to_nid, id_to_nid)
 

delphin/mrs/_mrs.py

@@ -290,7 +290,9 @@ def quantification_pairs(self):
                 pairs.append((ep, qmap.get(ep.iv)))
         # then unpaired quantifiers, if any
         for _, q in pairs:
-            if q is not None:
+            # some bad MRSs have multiple EPs share an ARG0; avoid the
+            # KeyError by checking if they are still in qmap
+            if q is not None and q.iv in qmap:
                 del qmap[q.iv]
         for q in qmap.values():
             pairs.append((None, q))