code: def get_columns(self, **kwargs) -> List[str]:
      column_list = []
      seen = set()
      for child in self.children:
          columns = child.get_columns(**kwargs)
          column_list.extend([f for f in columns if f not in seen])
          seen.update(columns)
      return column_list
  
imports: import hashlib
  import itertools
  from typing import Dict, List, Optional, Tuple, Union
  import numpy
  import pandas
  from pandas._typing import DtypeObj
  from upgini.autofe.all_operands import find_op
  from upgini.autofe.operand import Operand, PandasOperand
label_desc: Use image node_id 2 for calling the FeatureGroup obj's underlying member method code with example usage: obj.get_columns() and returns: column_list