added basic distributed logic for trainer

tests/nerf/configs/test_basic_graph.yaml

@@ -1,3 +1,4 @@
+world_size: 0
 network:
   mlp_0:
     class_name: MLP

tests/nerf/test_trainer.py

@@ -0,0 +1,15 @@
+from tty import CFLAG
+import pytest
+import runpy
+
+from mattport.nerf.trainer import Trainer
+from hydra import compose, initialize
+
+CONFIG_DIR = "configs"
+
+def test_multiprocess_train():
+    """Test for trainer to validate distributed data parallel working."""
+    with initialize(config_path=CONFIG_DIR):
+        cfg = compose(config_name='test_basic_graph')
+    trainer = Trainer(cfg)
+    trainer.run_multiprocess_train()