old_contents: # -*- coding: utf-8 -*-
  
  from .types import Closure
  
  """
  This module contains a few simple helper functions for
  checking the type of ASTs.
  """
  
  
  def is_symbol(x):
      return isinstance(x, str)
  
  
  def is_list(x):
      return isinstance(x, list)
  
  
  def is_boolean(x):
      return isinstance(x, bool)
  
  
  def is_integer(x):
      return isinstance(x, int)
  
  
  def is_closure(x):
      return isinstance(x, Closure)
  
  
  def is_atom(x):
      return is_symbol(x) \
          or is_integer(x) \
          or is_boolean(x) \
          or is_closure(x)
  
new_contents: # -*- coding: utf-8 -*-
  
  from .types import Closure
  
  """
  This module contains a few simple helper functions for
  checking the type of ASTs.
  """
  
  
  def is_symbol(x):
      return isinstance(x, str)
  
  
  def is_list(x):
      return isinstance(x, list)
  
  
  def is_boolean(x):
      return isinstance(x, bool)
  
  
  def is_integer(x):
      return isinstance(x, int)
  
  
  def is_closure(x):
      return isinstance(x, Closure)
  
  
  def is_atom(x):
      return (is_symbol(x) or
      	is_integer(x) or
      	is_boolean(x) or
      	is_closure(x))
  
subject: update is_atom function to follow PEP8