ensure columns are strings before concatenation (#1857)

Closes #1849

Ensures all columns are string columns prior to attempting string concatenation in `column_info.py`.

## By Submitting this PR I confirm:
- I am familiar with the [Contributing Guidelines](https://github.com/nv-morpheus/Morpheus/blob/main/docs/source/developer_guide/contributing.md).
- When the PR is ready for review, new or existing tests cover these changes.
- When the PR is ready for review, the documentation is up to date with these changes.

Authors:
  - Christopher Harris (https://github.com/cwharris)

Approvers:
  - Michael Demoret (https://github.com/mdemoret-nv)

URL: #1857

python/morpheus/morpheus/utils/column_info.py

@@ -469,9 +469,9 @@ def _process_column(self, df: pd.DataFrame) -> pd.Series:
             The processed column as a string Series.
         """
 
-        first_col = df[self.input_columns[0]]
+        first_col = df[self.input_columns[0]].astype(str)
 
-        return first_col.str.cat(others=df[self.input_columns[1:]], sep=self.sep)
+        return first_col.str.cat(others=df[self.input_columns[1:]].astype(str), sep=self.sep)
 
 
 @dataclasses.dataclass

tests/test_column_info.py

@@ -149,8 +149,11 @@ def test_string_cat_column():
                                               ],
                                               sep=", ")
 
-    with pytest.raises(Exception):
-        string_cat_col_with_int._process_column(df)
+    actual = string_cat_col_with_int._process_column(df)
+
+    expected = pd.Series(["New York, 10001", "Dallas, 75001", "Austin, 73301"])
+
+    assert actual.equals(expected)
 
 
 @pytest.mark.use_python