Add `accept.py` for test Filter

This `accept.py` also serves as an example for a module accept
accompanying the script `filter.py`.

Inst_eddies/Analysis/tests.json

@@ -121,6 +121,7 @@
 	    "$src_dir/Inst_eddies/Analysis/filter.py",
 	    "$PWD/Inst_eddies_4_anti",
 	    "plouf"
-	]
+	],
+	"env": {"PYTHONPATH": "$src_dir/Inst_eddies/Tests/Input"}
     }
 ]    

Inst_eddies/Tests/Input/accept.py

+def accept(shape_rec_extr, shape_rec_outer, shape_rec_max):
+    """Filtering function."""
+
+    ##return 0.125 <= shape_rec_extr.shape.points[0][0] <= 29.875 \
+    ##    and -59.875 <= shape_rec_extr.shape.points[0][1] <= -15.125
+    ##return shape_rec_extr.record.date == 20456
+    return shape_rec_extr.record.date == 20456 \
+        and shape_rec_extr.record.eddy_index == 87