def get_stream_xcorr(name_or_func=None, concurrency=None):
func = _get_registerd_func(name_or_func)<EOL>concur = concurrency or '<STR_LIT>'<EOL>if not hasattr(func, concur):<EOL><INDENT>msg = '<STR_LIT>' % (func.__name__, concur)<EOL>raise ValueError(msg)<EOL><DEDENT>return getattr(func, concur)<EOL>
Return a function for performing normalized cross correlation on lists of
streams.

:param name_or_func:
    Either a name of a registered function or a callable that implements
    the standard array_normxcorr signature.
:param concurrency:
    Optional concurrency strategy, options are below.

:return: A callable with the interface of stream_normxcorr

:Concurrency options:
    - multithread - use a threadpool for concurrency;
    - multiprocess - use a process pool for concurrency;
    - concurrent - use a customized concurrency strategy for the function,
      if not defined threading will be used.