code: def open(file, flag="c", mode=0o666):
      """Open the database file, filename, and return corresponding object.
  
      The flag argument, used to control how the database is opened in the
      other DBM implementations, supports only the semantics of 'c' and 'n'
      values.  Other values will default to the semantics of 'c' value:
      the database will always opened for update and will be created if it
      does not exist.
  
      The optional mode argument is the UNIX mode of the file, used only when
      the database has to be created.  It defaults to octal code 0o666 (and
      will be modified by the prevailing umask).
  
      """
  
      # Modify mode depending on the umask
      try:
          um = _os.umask(0)
          _os.umask(um)
      except AttributeError:
          pass
      else:
          # Turn off any bits that are set in the umask
          mode = mode & (~um)
      if flag not in ("r", "w", "c", "n"):
          raise ValueError("Flag must be one of 'r', 'w', 'c', or 'n'")
      return _Database(file, mode, flag=flag)
  
imports: import ast
  import io
  import os
  import collections.abc
label_desc: Use image node_id 1 for calling a global function with example usage: open(file, flag, mode) and returns: _Database