code: def triu(m, k=0, gpu=None):
      """
      Upper triangle of a tensor.
  
      Return a copy of a matrix with the elements below the `k`-th diagonal
      zeroed.
  
      Please refer to the documentation for `tril` for further details.
  
      See Also
      --------
      tril : lower triangle of a tensor
  
      Examples
      --------
      >>> import mars.tensor as mt
  
      >>> mt.triu([[1,2,3],[4,5,6],[7,8,9],[10,11,12]], -1).execute()
      array([[ 1,  2,  3],
             [ 4,  5,  6],
             [ 0,  8,  9],
             [ 0,  0, 12]])
  
      """
      m = astensor(m)
      gpu = m.op.gpu if gpu is None else gpu
      op = TensorTriu(k, dtype=m.dtype, sparse=m.issparse(), gpu=gpu)
      return op(m)
  
imports: import itertools
  import numpy
  from ...lib import sparse
  from ...None import opcodes
  from ...serialization.serializables import KeyField, Int32Field
  from ...utils import has_unknown_shape
  from ..array_utils import create_array
  from ..core import TensorOrder
  from .core import TensorHasInput
  from .zeros import TensorZeros
  from .array import tensor
label_desc: Use image node_id 1 for calling a global function with example usage: triu(m, k, gpu) and returns: op