code: def __init__(
      self,
      op: Operand,
      main_column: Optional[Union[Column, Feature]],
      children: List[Union[Column, Feature]],
  ):
      self.op = op
      self.main_column_node = main_column
      self.children = children
      self.data: Optional[pd.DataFrame] = None
  
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 1 to create a new FeatureGroup object  with example: obj = FeatureGroup(op, main_column, children)