change fetch to allow for local file selection (#1309)

test/extra/test_utils.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 import io, unittest
 import os
+import tempfile
 from unittest.mock import patch, MagicMock
 
 import torch
@@ -25,6 +26,27 @@ class TestFetch(unittest.TestCase):
     pimg = Image.open(io.BytesIO(img))
     assert pimg.size == (705, 1024)
 
+class TestFetchRelative(unittest.TestCase):
+  def setUp(self):
+    self.working_dir = os.getcwd()
+    self.tempdir = tempfile.TemporaryDirectory()
+    os.chdir(self.tempdir.name)
+    with open('test_file.txt', 'x') as f:
+        f.write("12345")
+  
+  def tearDown(self):
+    os.chdir(self.working_dir)
+    self.tempdir.cleanup()
+
+  #test ./
+  def test_fetch_relative_dotslash(self):
+    self.assertEqual(b'12345', fetch("./test_file.txt"))
+  
+  #test ../
+  def test_fetch_relative_dotdotslash(self):
+      os.mkdir('test_file_path')
+      os.chdir('test_file_path')
+      self.assertEqual(b'12345', fetch("../test_file.txt"))
 
 class TestDownloadFile(unittest.TestCase):
   def setUp(self):