code: def test_dgmm_incx_minus_one(self, dtype):
      if self.orderc != "F":
          pytest.skip()
      if cupy.cuda.runtime.is_hip:
          if self._check_dgmm_incx_minus_one_hip_skip_condition():
              pytest.xfail("HIP dgmm may have a bug")
      self._setup(dtype)
      if self.side == "L":
          ref = cupy.diag(self.x[::-1]) @ self.a
      elif self.side == "R":
          ref = self.a @ cupy.diag(self.x[::-1])
      c = cublas.dgmm(self.side, self.a, self.x, incx=-1)
      cupy.testing.assert_allclose(c, ref, rtol=self.tol, atol=self.tol)
  
imports: import numpy
  import pytest
  import cupy
  from cupy import cublas
  from cupy import testing
label_desc: Use image node_id 6 for calling the TestDgmm obj's underlying member method code with example usage: obj.test_dgmm_incx_minus_one(dtype) without return types