code: def unique(
      ary,
      is_equal_expr="a == b",
      extra_args=None,
      preamble="",
      queue=None,
      wait_for=None,
  ):
      """Copy the elements of *ary* into the output if *is_equal_expr*, applied to the
      array element and its predecessor, yields false.
  
      Works like the UNIX command :program:`uniq`, with a potentially custom
      comparison.  This operation is often used on sorted sequences.
  
      :arg is_equal_expr: a C expression evaluating to a ``bool``,
          represented as a string.  The elements being compared are
          available as ``a`` and ``b``. If this expression yields ``false``, the
          two are considered distinct.
      :arg extra_args: |scan_extra_args|
      :arg preamble: |preamble|
      :arg wait_for: |explain-waitfor|
      :returns: a tuple *(out, count, event)* where *out* is the output array, *count*
          is an on-device scalar (fetch to host with ``count.get()``) indicating
          how many elements satisfied the predicate, and *event* is a
          :class:`pyopencl.Event` for dependency management.
  
      .. versionadded:: 2013.1
      """
  
      if len(ary) > np.iinfo(np.uint32).max:
          scan_dtype = np.uint64
      else:
          scan_dtype = np.uint32
  
      if wait_for is None:
          wait_for = []
  
      (
          extra_args_types,
          extra_args_values,
          extra_wait_for,
      ) = _extract_extra_args_types_values(extra_args)
      wait_for = wait_for + extra_wait_for
  
      knl = _unique_template.build(
          ary.context,
          type_aliases=(("item_t", ary.dtype), ("scan_t", scan_dtype)),
          var_values=(("macro_is_equal_expr", is_equal_expr),),
          more_preamble=preamble,
          more_arguments=extra_args_types,
      )
  
      out = cl.array.empty_like(ary)
      count = ary._new_with_changes(
          data=None, offset=0, shape=(), strides=(), dtype=scan_dtype
      )
  
      evt = knl(
          ary,
          out,
          count,
          *extra_args_values,
          queue=queue,
          wait_for=wait_for,
      )
  
      return out, count, evt
  
imports: from dataclasses import dataclass
  from typing import Optional
  import numpy
  import pyopencl
  import pyopencl.array
  from pyopencl.elementwise import ElementwiseKernel
  from pyopencl.scan import ScanTemplate, GenericScanKernel
  from pyopencl.tools import dtype_to_ctype, get_arg_offset_adjuster_code
  from pytools import memoize, memoize_method
  from mako.template import Template
label_desc: Use image node_id 5 for calling a global function with example usage: unique(ary, is_equal_expr, extra_args, preamble, queue, wait_for) and returns: out,  count,  evt