A new causal mechanism qualifier for "guanyl_nucleotide_exchange" was…

… added to Biolink

This helps address one of the gaps seen in the SIGNOR database edge properties.

parsers/SIGNOR/src/signor_mechanism_predicate_mapping.py

@@ -71,6 +71,9 @@
 
             # This probably needs to be a node property.
             "guanine nucleotide exchange factor": {
+            	"edge_properties": {
+                                    CAUSAL_MECHANISM_QUALIFIER: "guanyl_nucleotide_exchange"
+		}
             },
 
             "post transcriptional modification": {
@@ -220,4 +223,4 @@
             OBJECT_ASPECT_QUALIFIER: "expression"
         }
     }
-}
+}