change: correct code per len-as-condition Pylint check (aws#902)

The Pylint check is not actually enabled in this commit as it conflicts
directly with NumPy. Pylint has corrected this, and it will be included
in their next release (2.4.0):
pylint-dev/pylint#2684

Once Pylint 2.4.0 is released, we can consume it and remove this check.
A summary of this information is included in a TODO near the relevant
Pylint disable rule (len-as-condition).

Author: knakad

.pylintrc

@@ -82,7 +82,7 @@ disable=
     invalid-name,
     too-many-instance-attributes,
     line-too-long, # We let Flake8 take care of this # TODO: Fix these and stop relying on flake8
-    len-as-condition, # TODO: Use if seq: and if not seq: instead
+    len-as-condition, # TODO: Enable this check once pylint 2.4.0 is released and consumed due to the fix in https://github.com/PyCQA/pylint/issues/2684
     logging-format-interpolation, # TODO: Fix logging so as to remove this.
     import-error, # TODO: Fix import errors
     logging-not-lazy, # TODO: Fix logging

src/sagemaker/predictor.py

@@ -195,7 +195,7 @@ def _serialize_row(data):
         if isinstance(data, np.ndarray):
             data = np.ndarray.flatten(data)
         if hasattr(data, "__len__"):
-            if len(data):
+            if len(data) > 0:
                 return _csv_serialize_python_array(data)
             else:
                 raise ValueError("Cannot serialize empty array")