code: def flatten(a):
      """
      Recursively flatten tuple, list and set in a list.
  
      """
      if isinstance(a, (tuple, list, set)):
          l = []
          for item in a:
              l.extend(flatten(item))
          return l
      else:
          return [a]
  
imports: from __future__ import absolute_import, print_function, division
  import linecache
  import sys
  import traceback
  import numpy
  from six import iteritems, integer_types, string_types, with_metaclass
  from six.moves import StringIO
  from theano import config
  from theano.compat import PY3
label_desc: Use image node_id 14 for calling a global function with example usage: flatten(a) and returns: l, list