class_docstr: Sqlite backed document storage.
  
  Implements get_doc_text(doc_id).
docstr: Fetch all ids of docs stored in the db.
code: def get_doc_ids(self):
      """
      Fetch all ids of docs stored in the db.
      """
      cursor = self.connection.cursor()
      cursor.execute("SELECT id FROM documents")
      results = [r[0] for r in cursor.fetchall()]
      cursor.close()
      return results
  
file_path: ParlAI/parlai/agents/tfidf_retriever/doc_db.py
imports: import sqlite3
  from .None import utils
label_desc: Use image node_id 5 for calling the DocDB obj's underlying member method code with example usage: obj.get_doc_ids() and returns: results