code: def get_reduction_callable(cls, op):
      skipna, ddof = op.skipna, op.ddof
  
      def sem(x):
          var = x.var(skipna=skipna, ddof=ddof)
          cnt = x.count()
          return (var / cnt) ** 0.5
  
      return sem
  
file_path: mars/mars/dataframe/reduction/sem.py
imports: from ...None import opcodes
  from ...config import options
  from ...core import OutputType
  from ...serialization.serializables import Int32Field
  from .core import DataFrameReductionOperand, DataFrameReductionMixin
label_desc: Use image node_id 3 for calling the DataFrameSem obj's underlying member method code with example usage: obj.get_reduction_callable(cls, op) and returns: sem, unknown