Simplify to remove getattr(pa, "array", None) call

Co-Authored-By: Dongdong Tian <seisman.info@gmail.com>

Author: weiji14

pygmt/tests/test_clib_virtualfile_from_vectors.py

@@ -15,8 +15,10 @@
 
 try:
     import pyarrow as pa
+
+    pa_array = pa.array
 except ImportError:
-    pa = None
+    pa_array = None
 
 
 @pytest.fixture(scope="module", name="dtypes")
@@ -65,8 +67,8 @@ def test_virtualfile_from_vectors(dtypes):
         pytest.param(np.array, {"dtype": np.str_}, id="str"),
         pytest.param(np.array, {"dtype": np.object_}, id="object"),
         pytest.param(
-            getattr(pa, "array", None),
-            {},  # pa.string()
+            pa_array,
+            {},  # {"type": pa.string()}
             marks=skip_if_no(package="pyarrow"),
             id="pyarrow",
         ),