fix: catch import error in older sqlalchemy versions

Signed-off-by: Erik Wrede <erikwrede2@gmail.com>

Author: erikwrede

graphene_sqlalchemy/converter.py

@@ -8,7 +8,7 @@
 from sqlalchemy import types as sqa_types
 from sqlalchemy.dialects import postgresql
 from sqlalchemy.ext.hybrid import hybrid_property
-from sqlalchemy.orm import MapperProperty, interfaces, strategies
+from sqlalchemy.orm import interfaces, strategies
 
 import graphene
 from graphene.types.json import JSONString
@@ -27,6 +27,13 @@
     value_equals_strict,
 )
 
+# We just use MapperProperties for type hints, they don't exist in sqlalchemy < 1.4
+try:
+    from sqlalchemy import MapperProperty
+except ImportError:
+    # sqlalchemy < 1.4
+    MapperProperty = Any
+
 try:
     from typing import ForwardRef
 except ImportError: