code: def fit(self, ctx: Context, train_data, validate_data=None) -> None:
      if self.select_col is None:
          self.select_col = train_data.schema.columns.to_list()
      train_data_select = train_data[self.select_col]
      self._mean = train_data_select.mean()
      self._std = train_data_select.std()
  
imports: import logging
  import pandas
  from fate.arch import Context
  from ..abc.module import Module
label_desc: Use image node_id 2 for calling the StandardScaler obj's underlying member method code with example usage: obj.fit(ctx, train_data, validate_data) without return types