code: def test_getitem(self):
      dtype = np.dtype(
          [
              ("position", np.float32, 3),
              ("texcoord", np.float32, 2),
              ("color", np.float32, 4),
          ]
      )
      data = np.zeros(10, dtype=dtype)
      B = DataBuffer(data)
      assert B[1].dtype == dtype
      assert B[1].size == 1
      assert B[-1].dtype == dtype
      assert B[-1].size == 1
  
      self.assertRaises(IndexError, B.__getitem__, +999)
      self.assertRaises(IndexError, B.__getitem__, -999)
  
imports: import unittest
  import numpy
  from vispy.testing import run_tests_if_main
  from vispy.gloo.buffer import Buffer, DataBuffer, DataBufferView, VertexBuffer, IndexBuffer
label_desc: Use image node_id 11 for calling the DataBufferTest obj's underlying member method code with example usage: obj.test_getitem() without return types