add unique function (#797)

* add unique function

Author: KsanaKozlova

dpnp/dpnp_iface_manipulation.py

@@ -67,6 +67,7 @@
     "stack",
     "swapaxes",
     "transpose",
+    "unique",
     "vstack"
 ]
 
@@ -619,6 +620,25 @@ def transpose(x1, axes=None):
     return call_origin(numpy.transpose, x1, axes=axes)
 
 
+def unique(x1, **kwargs):
+    """
+    Find the unique elements of an array.
+
+    For full documentation refer to :obj:`numpy.unique`.
+
+    Examples
+    --------
+    >>> import dpnp as np
+    >>> x = np.array([1, 1, 2, 2, 3, 3])
+    >>> res = np.unique(x)
+    >>> print(res)
+    [1, 2, 3]
+
+    """
+
+    return call_origin(numpy.unique, x1, **kwargs)
+
+
 def vstack(tup):
     """
     Stack arrays in sequence vertically (row wise).

tests/test_manipulation.py

@@ -32,3 +32,21 @@ def test_repeat(arr):
     expected = numpy.repeat(a, 2)
     result = dpnp.repeat(dpnp_a, 2)
     numpy.testing.assert_array_equal(expected, result)
+
+
+@pytest.mark.parametrize("array",
+                         [[1, 2, 3],
+                          [1, 2, 2, 1, 2, 4],
+                          [2, 2, 2, 2],
+                          []],
+                         ids=['[1, 2, 3]',
+                              '[1, 2, 2, 1, 2, 4]',
+                              '[2, 2, 2, 2]',
+                              '[]'])
+def test_unique(array):
+    np_a = numpy.array(array)
+    dpnp_a = dpnp.array(array)
+
+    expected = numpy.unique(np_a)
+    result = dpnp.unique(dpnp_a)
+    numpy.testing.assert_array_equal(expected, result)