docstr: Instantiate a TinyDbObserver with an existing db and filesystem.
docstr_tok: ["Instantiate","a","TinyDbObserver","with","an","existing","db","and","filesystem","."]
code: def create_from(cls, db, fs, overwrite=None, root=None):
      """Instantiate a TinyDbObserver with an existing db and filesystem."""
      self = cls.__new__(cls)  # skip __init__ call
      self.db = db
      self.runs = db.table("runs")
      self.fs = fs
      self.overwrite = overwrite
      self.run_entry = {}
      self.db_run_id = None
      self.root = root
      return self
  
imports: from __future__ import division, print_function, unicode_literals, absolute_import
  import os
  import textwrap
  import uuid
  from collections import OrderedDict
  import warnings
  from sacred.__about__ import __version__
  from sacred.commandline_options import cli_option
  from sacred.observers import RunObserver
label_desc: Use image node_id 3 for calling the TinyDbObserver obj's underlying member method code with example usage: obj.create_from(cls, db, fs, overwrite, root) and returns: self