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import sys

PY3 = sys.version_info[0] >= 3

if PY3:  # pragma: no cover
    basestring = str
    unicode_type = str
    bytes_type = bytes

    def iteritems(d):
        return iter(d.items())

    def itervalues(d):
        return iter(d.values())

    range = range
    zip = zip
    from functools import reduce
    import builtins
    from urllib.request import urlretrieve
else:  # pragma: no cover
    # Python 2
    basestring = basestring
    unicode_type = unicode
    bytes_type = str

    def iteritems(d):
        return d.iteritems()

    def itervalues(d):
        return d.itervalues()

    range = xrange
    from itertools import izip as zip, imap as map
    reduce = reduce
    import __builtin__ as builtins
    from urllib import urlretrieve

try:
    from cyordereddict import OrderedDict
except ImportError:  # pragma: no cover
    try:
        from collections import OrderedDict
    except ImportError:
        from ordereddict import OrderedDict

try:
    # solely for isinstance checks
    import dask.array
    dask_array_type = (dask.array.Array,)
except ImportError:  # pragma: no cover
    dask_array_type = ()

try:
    from contextlib import suppress
except ImportError:
    # backport from Python 3.5:
    class suppress:
        """Context manager to suppress specified exceptions

        After the exception is suppressed, execution proceeds with the next
        statement following the with statement.

             with suppress(FileNotFoundError):
                 os.remove(somefile)
             # Execution still resumes here if the file was already removed
        """

        def __init__(self, *exceptions):
            self._exceptions = exceptions

        def __enter__(self):
            pass

        def __exit__(self, exctype, excinst, exctb):
            # Unlike isinstance and issubclass, CPython exception handling
            # currently only looks at the concrete type hierarchy (ignoring
            # the instance and subclass checking hooks). While Guido considers
            # that a bug rather than a feature, it's a fairly hard one to fix
            # due to various internal implementation details. suppress provides
            # the simpler issubclass based semantics, rather than trying to
            # exactly reproduce the limitations of the CPython interpreter.
            #
            # See http://bugs.python.org/issue12029 for more details
            return exctype is not None and issubclass(exctype, self._exceptions)