text: # coding: utf-8
  
  truthy = frozenset(('t', 'true', 'y', 'yes', 'on', '1'))
  
  
  def asbool(s):
      """ Return the boolean value ``True`` if the case-lowered value of string
      input ``s`` is a :term:`truthy string`. If ``s`` is already one of the
      boolean values ``True`` or ``False``, return it."""
      if s is None:
          return False
      if isinstance(s, bool):
          return s
      s = str(s).strip()
      return s.lower() in truthy
  