assert to prepare for grad uop [pr] (#8280)

* assert to prepare for grad uop [pr]

* fix test_nn

* fix most of test_tensor

* few more tests

* fix multi

* uniform gradient

* acc_dtype

* any for multi

* fix typing

* fix assert, CAST_BEFORE_VIEW is still the issue

* explict test for CAST_BEFORE_VIEW

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Co-authored-by: qazal <77887910+Qazalin@users.noreply.github.com>

test/test_tensor.py

@@ -464,7 +464,7 @@ class TestTinygrad(unittest.TestCase):
   def test_repr_with_grad(self):
     a = Tensor([1], requires_grad=True)
     b = Tensor([1])
-    c = (a + b).mean().backward()
+    c = (a + b).sum().backward()
     print(a)
     print(c)