docstr: Returns
  -------
  dt : pd.Timestamp
      The first trading day (session) for which the reader can provide
      data.
docstr_tok: ["Returns","--","--","--","-","dt",":","pd.Timestamp","The","first","trading","day","(","session",")","for","which","the","reader","can","provide","data","."]
code: def first_trading_day(self):
      """
      Returns
      -------
      dt : pd.Timestamp
          The first trading day (session) for which the reader can provide
          data.
      """
      pass
  
file_path: catalyst/catalyst/data/bar_reader.py
imports: from abc import ABCMeta, abstractmethod, abstractproperty
  from six import with_metaclass
label_desc: Use image node_id 5 for calling the BarReader obj's underlying member method code with example usage: obj.first_trading_day() without return types