code: def ddof(self):
      return self._ddof
  
file_path: mars/mars/dataframe/reduction/var.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 2 for calling the DataFrameVar obj's underlying member method code with example usage: obj.ddof() and returns: self