Harrison/memory check (#2119)

Co-authored-by: JIAQIA <jqq1716@gmail.com>

langchain/chains/sequential.py

@@ -46,8 +46,8 @@ class SequentialChain(Chain, BaseModel):
         if "memory" in values and values["memory"] is not None:
             """Validate that prompt input variables are consistent."""
             memory_keys = values["memory"].memory_variables
-            if any(input_variables) in memory_keys:
-                overlapping_keys = input_variables & memory_keys
+            if set(input_variables).intersection(set(memory_keys)):
+                overlapping_keys = set(input_variables) & set(memory_keys)
                 raise ValueError(
                     f"The the input key(s) {''.join(overlapping_keys)} are found "
                     f"in the Memory keys ({memory_keys}) - please use input and "

tests/unit_tests/chains/test_sequential.py

@@ -68,6 +68,13 @@ def test_sequential_usage_memory() -> None:
     output = chain({"foo": "123"})
     expected_output = {"baz": "123foofoo", "foo": "123", "zab": "rab"}
     assert output == expected_output
+    memory = SimpleMemory(memories={"zab": "rab", "foo": "rab"})
+    chain_1 = FakeChain(input_variables=["foo"], output_variables=["bar"])
+    chain_2 = FakeChain(input_variables=["bar"], output_variables=["baz"])
+    with pytest.raises(ValueError):
+        SequentialChain(
+            memory=memory, chains=[chain_1, chain_2], input_variables=["foo"]
+        )
 
 
 def test_sequential_usage_multiple_outputs() -> None: