code: def iterkeys(self):
      try:
          return iter(self._index)
      except TypeError:
          raise error("DBM object has already been closed") from None
  
imports: import ast
  import io
  import os
  import collections.abc
label_desc: Use image node_id 15 for calling the _Database obj's underlying member method code with example usage: obj.iterkeys() and returns: iter