code: def to_cpu(x):
      x = astensor(x)
  
      if x.op.gpu is False:
          return x
  
      op = TensorToCPU(dtype=x.dtype)
      return op(x)
  
file_path: mars/mars/tensor/base/to_cpu.py
imports: from ...None import opcodes
  from ..datasource import tensor
  from .core import TensorDeviceConversionBase
label_desc: Use image node_id 1 for calling a global function with example usage: to_cpu(x) and returns: op, x