class_docstr: Sqlite backed document storage.
  
  Implements get_doc_text(doc_id).
code: def __enter__(self):
      return self
  
file_path: ParlAI/parlai/agents/tfidf_retriever/doc_db.py
imports: import sqlite3
  from .None import utils
label_desc: Use image node_id 2 for calling the DocDB obj's underlying member method code with example usage: obj.__enter__() and returns: self