docstr: A proxy-call to the dataframe's `.isna()`.
code: def isna(self):
      """
      A proxy-call to the dataframe's `.isna()`.
      """
      return self.dataframe.isna()
  
imports: from abc import ABC
label_desc: Use image node_id 11 for calling the DataframeAbstract obj's underlying member method code with example usage: obj.isna() and returns: self