237 def flatten(thing):

   238     """Yield a single stream from a possibly nested set of iterators"""

   239     thing = unwraphybrid(thing)

   240     if isinstance(thing, bytes):

   241         yield thing

   242     elif isinstance(thing, str):

   243         # We can only hit this on Python 3, and it's here to guard

   244         # against infinite recursion.

   245         raise error.ProgrammingError('Mercurial IO including templates is done'

   246                                      ' with bytes, not strings, got %r' % thing)

   247     elif thing is None:

   248         pass

   249     elif not util.safehasattr(thing, '__iter__'):

   250         yield pycompat.bytestr(thing)

   251     else:

   252         for i in thing:

   253             i = unwraphybrid(i)

   254             if isinstance(i, bytes):

   255                 yield i

   256             elif i is None:

   257                 pass

   258             elif not util.safehasattr(i, '__iter__'):

   259                 yield pycompat.bytestr(i)

   260             else:

   261                 for j in flatten(i):

   262                     yield j

   263