class_docstr: DataSource which loads data from a pandas DataFrame.
  
  Inputs:
      train_df: DataFrame for training
  
      eval_df: DataFrame for evalu
  
      test_df: DataFrame for test
  
      schema: same as base DataSource, define the list of output values with their types
  
      column_mapping: maps the column names in DataFrame to the name defined in schema
code: def raw_eval_data_generator(self):
      return self.raw_generator(self.eval_df)
  
file_path: pytext/pytext/data/sources/pandas.py
imports: from typing import Dict, Optional, Type
  from pandas import DataFrame
  from pytext.data.sources.data_source import RootDataSource
  from .session import SessionDataSource
label_desc: Use image node_id 5 for calling the PandasDataSource obj's underlying member method code with example usage: obj.raw_eval_data_generator() and returns: self