[yaml] - fix post commit yaml test

.github/trigger_files/beam_PostCommit_Yaml_Xlang_Direct.json

@@ -1,4 +1,4 @@
 {
   "comment": "Modify this file in a trivial way to cause this test suite to run",
-  "revision": 1
+  "revision": 2
 }

.github/trigger_files/beam_PreCommit_Yaml_Xlang_Direct.json

@@ -1,4 +1,4 @@
 {
     "comment": "Modify this file in a trivial way to cause this test suite to run",
-    "revision": 2
+    "revision": 3
 }

sdks/python/apache_beam/yaml/extended_tests/e2e/gcs_avro_to_cloud_bigtable.yaml

@@ -64,19 +64,19 @@ pipelines:
               key:
                 callable: |
                   def convert_to_bytes(row):
-                    return bytes(row.key, 'utf-8') if "key" in row._fields else None
+                    return bytes(row.key, 'utf-8') if hasattr(row, "key") else None
               type:
                 type
               family_name:
                 family_name
               column_qualifier:
                 callable: |
                   def convert_to_bytes(row):
-                    return bytes(row.column_qualifier, 'utf-8') if 'column_qualifier' in row._fields else None
+                    return bytes(row.column_qualifier, 'utf-8') if hasattr(row, 'column_qualifier') else None
               value:
                 callable: |
                   def convert_to_bytes(row):
-                    return bytes(row.value, 'utf-8') if 'value' in row._fields else None
+                    return bytes(row.value, 'utf-8') if hasattr(row, 'value') else None
               timestamp_micros:
                 timestamp_micros
         - type: WriteToBigTable
@@ -102,13 +102,13 @@ pipelines:
               key:
                 callable: |
                   def convert_to_string(row):
-                    return row.key.decode("utf-8") if "key" in row._fields else None
+                    return row.key.decode("utf-8") if hasattr(row, "key") else None
               family_name:
                 family_name
               column_qualifier:
                 callable: |
                   def convert_to_string(row):
-                    return row.column_qualifier.decode("utf-8") if "column_qualifier" in row._fields else None
+                    return row.column_qualifier.decode("utf-8") if hasattr(row, "column_qualifier") else None
               cells:
                 callable: |
                   def convert_to_string(row):