Fix(sqlite): allow 2-arg version of UNHEX closes #4648

Author: georgesittas

sqlglot/expressions.py

@@ -6679,7 +6679,7 @@ class TsOrDiToDi(Func):
 
 
 class Unhex(Func):
-    pass
+    arg_types = {"this": True, "expression": False}
 
 
 class Unicode(Func):

tests/dialects/test_sqlite.py

@@ -7,6 +7,7 @@ class TestSQLite(Validator):
     dialect = "sqlite"
 
     def test_sqlite(self):
+        self.validate_identity("UNHEX(a, b)")
         self.validate_identity("SELECT DATE()")
         self.validate_identity("SELECT DATE('now', 'start of month', '+1 month', '-1 day')")
         self.validate_identity("SELECT DATETIME(1092941466, 'unixepoch')")