prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  cytoolz is required to import blaze, but it's not listed in requirements_strict.txt
  In a fresh virtualenv, `pip install blaze && python -c "import blaze"` fails with:
  
  ```
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    File "/home/ssanderson/.virtualenvs/blaze/local/lib/python2.7/site-packages/blaze/__init__.py", line 18, in <module>
      from .utils import ignoring
    File "/home/ssanderson/.virtualenvs/blaze/local/lib/python2.7/site-packages/blaze/utils.py", line 7, in <module>
      from cytoolz import nth
  ImportError: No module named cytoolz
  ```
  
  Is there a reason cytoolz isn't in the strict requirements if it's necessary to even import the top-level module?
  
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `blaze/utils.py`
  Content:
  ```
  1 from __future__ import absolute_import, division, print_function
  2 
  3 import os
  4 import datetime
  5 from functools import wraps
  6 
  7 from cytoolz import nth
  8 from itertools import islice
  9 from collections import Iterator
  10 from multiprocessing.pool import ThreadPool
  11 
  12 # these are used throughout blaze, don't remove them
  13 from odo.utils import tmpfile, filetext, filetexts, raises, keywords, ignoring
  14 
  15 import psutil
  16 import numpy as np
  17 
  18 # Imports that replace older utils.
  19 from .compatibility import map, zip
  20 
  21 from .dispatch import dispatch
  22 
  23 thread_pool = ThreadPool(psutil.NUM_CPUS)
  24 
  25 
  26 def nth_list(n, seq):
  27     """
  28 
  29     >>> tuple(nth_list([0, 1, 4], 'Hello'))
  30     ('H', 'e', 'o')
  31     >>> tuple(nth_list([4, 1, 0], 'Hello'))
  32     ('o', 'e', 'H')
  33     >>> tuple(nth_list([0, 0, 0], 'Hello'))
  34     ('H', 'H', 'H')
  35     """
  36     seq = iter(seq)
  37 
  38     result = []
  39     old = 0
  40     item = next(seq)
  41     for index in sorted(n):
  42         for i in range(index - old):
  43             item = next(seq)
  44         result.append(item)
  45         old = index
  46 
  47     order = [x[1] for x in sorted(zip(n, range(len(n))))]
  48     return (result[i] for i in order)
  49 
  50 
  51 def get(ind, coll, lazy=False):
  52     """
  53 
  54     >>> get(0, 'Hello')
  55     'H'
  56 
  57     >>> get([1, 0], 'Hello')
  58     ('e', 'H')
  59 
  60     >>> get(slice(1, 4), 'Hello')
  61     ('e', 'l', 'l')
  62 
  63     >>> get(slice(1, 4), 'Hello', lazy=True)
  64     <itertools.islice object at ...>
  65     """
  66     if isinstance(ind, list):
  67         result = nth_list(ind, coll)
  68     elif isinstance(ind, slice):
  69         result = islice(coll, ind.start, ind.stop, ind.step)
  70     else:
  71         if isinstance(coll, Iterator):
  72             result = nth(ind, coll)
  73         else:
  74             result = coll[ind]
  75     if not lazy and isinstance(result, Iterator):
  76         result = tuple(result)
  77     return result
  78 
  79 
  80 def ndget(ind, data):
  81     """
  82     Get from N-Dimensional getable
  83 
  84     Can index with elements, lists, or slices.  Mimic's numpy fancy indexing on
  85     generic indexibles.
  86 
  87     >>> data = [[[1, 2], [3, 4]], [[5, 6], [7, 8]]]
  88     >>> ndget(0, data)
  89     [[1, 2], [3, 4]]
  90     >>> ndget((0, 1), data)
  91     [3, 4]
  92     >>> ndget((0, 0, 0), data)
  93     1
  94     >>> ndget((slice(0, 2), [0, 1], 0), data)
  95     ((1, 3), (5, 7))
  96     """
  97     if isinstance(ind, tuple) and len(ind) == 1:
  98         ind = ind[0]
  99     if not isinstance(ind, tuple):
  100         return get(ind, data)
  101     result = get(ind[0], data)
  102     if isinstance(ind[0], (list, slice)):
  103         return type(result)(ndget(ind[1:], row) for row in result)
  104     else:
  105         return ndget(ind[1:], result)
  106 
  107 
  108 def normalize_to_date(dt):
  109     if isinstance(dt, datetime.datetime) and not dt.time():
  110         return dt.date()
  111     else:
  112         return dt
  113 
  114 
  115 def assert_allclose(lhs, rhs):
  116     for tb in map(zip, lhs, rhs):
  117         for left, right in tb:
  118             if isinstance(left, (np.floating, float)):
  119                 # account for nans
  120                 assert np.all(np.isclose(left, right, equal_nan=True))
  121                 continue
  122             if isinstance(left, datetime.datetime):
  123                 left = normalize_to_date(left)
  124             if isinstance(right, datetime.datetime):
  125                 right = normalize_to_date(right)
  126             assert left == right
  127 
  128 
  129 def example(filename, datapath=os.path.join('examples', 'data')):
  130     import blaze
  131     return os.path.join(os.path.dirname(blaze.__file__), datapath, filename)
  132 
  133 
  134 def available_memory():
  135     return psutil.virtual_memory().available
  136 
  137 
  138 def listpack(x):
  139     """
  140     >>> listpack(1)
  141     [1]
  142     >>> listpack((1, 2))
  143     [1, 2]
  144     >>> listpack([1, 2])
  145     [1, 2]
  146     """
  147     if isinstance(x, tuple):
  148         return list(x)
  149     elif isinstance(x, list):
  150         return x
  151     else:
  152         return [x]
  153 
  154 
  155 @dispatch(datetime.datetime)
  156 def json_dumps(dt):
  157     s = dt.isoformat()
  158     if not dt.tzname():
  159         s = s + 'Z'
  160     return s
  161
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/blaze/utils.py b/blaze/utils.py
  --- a/blaze/utils.py
  +++ b/blaze/utils.py
  @@ -4,7 +4,11 @@
   import datetime
   from functools import wraps
   
  -from cytoolz import nth
  +try:
  +    from cytoolz import nth
  +except ImportError:
  +    from toolz import nth
  +
   from itertools import islice
   from collections import Iterator
   from multiprocessing.pool import ThreadPool
  
verification_info: {"golden_diff": "diff --git a/blaze/utils.py b/blaze/utils.py\n--- a/blaze/utils.py\n+++ b/blaze/utils.py\n@@ -4,7 +4,11 @@\n import datetime\n from functools import wraps\n \n-from cytoolz import nth\n+try:\n+    from cytoolz import nth\n+except ImportError:\n+    from toolz import nth\n+\n from itertools import islice\n from collections import Iterator\n from multiprocessing.pool import ThreadPool\n", "issue": "cytoolz is required to import blaze, but it's not listed in requirements_strict.txt\nIn a fresh virtualenv, `pip install blaze && python -c \"import blaze\"` fails with:\n\n```\nTraceback (most recent call last):\n  File \"<stdin>\", line 1, in <module>\n  File \"/home/ssanderson/.virtualenvs/blaze/local/lib/python2.7/site-packages/blaze/__init__.py\", line 18, in <module>\n    from .utils import ignoring\n  File \"/home/ssanderson/.virtualenvs/blaze/local/lib/python2.7/site-packages/blaze/utils.py\", line 7, in <module>\n    from cytoolz import nth\nImportError: No module named cytoolz\n```\n\nIs there a reason cytoolz isn't in the strict requirements if it's necessary to even import the top-level module?\n\n", "before_files": [{"content": "from __future__ import absolute_import, division, print_function\n\nimport os\nimport datetime\nfrom functools import wraps\n\nfrom cytoolz import nth\nfrom itertools import islice\nfrom collections import Iterator\nfrom multiprocessing.pool import ThreadPool\n\n# these are used throughout blaze, don't remove them\nfrom odo.utils import tmpfile, filetext, filetexts, raises, keywords, ignoring\n\nimport psutil\nimport numpy as np\n\n# Imports that replace older utils.\nfrom .compatibility import map, zip\n\nfrom .dispatch import dispatch\n\nthread_pool = ThreadPool(psutil.NUM_CPUS)\n\n\ndef nth_list(n, seq):\n    \"\"\"\n\n    >>> tuple(nth_list([0, 1, 4], 'Hello'))\n    ('H', 'e', 'o')\n    >>> tuple(nth_list([4, 1, 0], 'Hello'))\n    ('o', 'e', 'H')\n    >>> tuple(nth_list([0, 0, 0], 'Hello'))\n    ('H', 'H', 'H')\n    \"\"\"\n    seq = iter(seq)\n\n    result = []\n    old = 0\n    item = next(seq)\n    for index in sorted(n):\n        for i in range(index - old):\n            item = next(seq)\n        result.append(item)\n        old = index\n\n    order = [x[1] for x in sorted(zip(n, range(len(n))))]\n    return (result[i] for i in order)\n\n\ndef get(ind, coll, lazy=False):\n    \"\"\"\n\n    >>> get(0, 'Hello')\n    'H'\n\n    >>> get([1, 0], 'Hello')\n    ('e', 'H')\n\n    >>> get(slice(1, 4), 'Hello')\n    ('e', 'l', 'l')\n\n    >>> get(slice(1, 4), 'Hello', lazy=True)\n    <itertools.islice object at ...>\n    \"\"\"\n    if isinstance(ind, list):\n        result = nth_list(ind, coll)\n    elif isinstance(ind, slice):\n        result = islice(coll, ind.start, ind.stop, ind.step)\n    else:\n        if isinstance(coll, Iterator):\n            result = nth(ind, coll)\n        else:\n            result = coll[ind]\n    if not lazy and isinstance(result, Iterator):\n        result = tuple(result)\n    return result\n\n\ndef ndget(ind, data):\n    \"\"\"\n    Get from N-Dimensional getable\n\n    Can index with elements, lists, or slices.  Mimic's numpy fancy indexing on\n    generic indexibles.\n\n    >>> data = [[[1, 2], [3, 4]], [[5, 6], [7, 8]]]\n    >>> ndget(0, data)\n    [[1, 2], [3, 4]]\n    >>> ndget((0, 1), data)\n    [3, 4]\n    >>> ndget((0, 0, 0), data)\n    1\n    >>> ndget((slice(0, 2), [0, 1], 0), data)\n    ((1, 3), (5, 7))\n    \"\"\"\n    if isinstance(ind, tuple) and len(ind) == 1:\n        ind = ind[0]\n    if not isinstance(ind, tuple):\n        return get(ind, data)\n    result = get(ind[0], data)\n    if isinstance(ind[0], (list, slice)):\n        return type(result)(ndget(ind[1:], row) for row in result)\n    else:\n        return ndget(ind[1:], result)\n\n\ndef normalize_to_date(dt):\n    if isinstance(dt, datetime.datetime) and not dt.time():\n        return dt.date()\n    else:\n        return dt\n\n\ndef assert_allclose(lhs, rhs):\n    for tb in map(zip, lhs, rhs):\n        for left, right in tb:\n            if isinstance(left, (np.floating, float)):\n                # account for nans\n                assert np.all(np.isclose(left, right, equal_nan=True))\n                continue\n            if isinstance(left, datetime.datetime):\n                left = normalize_to_date(left)\n            if isinstance(right, datetime.datetime):\n                right = normalize_to_date(right)\n            assert left == right\n\n\ndef example(filename, datapath=os.path.join('examples', 'data')):\n    import blaze\n    return os.path.join(os.path.dirname(blaze.__file__), datapath, filename)\n\n\ndef available_memory():\n    return psutil.virtual_memory().available\n\n\ndef listpack(x):\n    \"\"\"\n    >>> listpack(1)\n    [1]\n    >>> listpack((1, 2))\n    [1, 2]\n    >>> listpack([1, 2])\n    [1, 2]\n    \"\"\"\n    if isinstance(x, tuple):\n        return list(x)\n    elif isinstance(x, list):\n        return x\n    else:\n        return [x]\n\n\n@dispatch(datetime.datetime)\ndef json_dumps(dt):\n    s = dt.isoformat()\n    if not dt.tzname():\n        s = s + 'Z'\n    return s\n", "path": "blaze/utils.py"}], "after_files": [{"content": "from __future__ import absolute_import, division, print_function\n\nimport os\nimport datetime\nfrom functools import wraps\n\ntry:\n    from cytoolz import nth\nexcept ImportError:\n    from toolz import nth\n\nfrom itertools import islice\nfrom collections import Iterator\nfrom multiprocessing.pool import ThreadPool\n\n# these are used throughout blaze, don't remove them\nfrom odo.utils import tmpfile, filetext, filetexts, raises, keywords, ignoring\n\nimport psutil\nimport numpy as np\n\n# Imports that replace older utils.\nfrom .compatibility import map, zip\n\nfrom .dispatch import dispatch\n\nthread_pool = ThreadPool(psutil.NUM_CPUS)\n\n\ndef nth_list(n, seq):\n    \"\"\"\n\n    >>> tuple(nth_list([0, 1, 4], 'Hello'))\n    ('H', 'e', 'o')\n    >>> tuple(nth_list([4, 1, 0], 'Hello'))\n    ('o', 'e', 'H')\n    >>> tuple(nth_list([0, 0, 0], 'Hello'))\n    ('H', 'H', 'H')\n    \"\"\"\n    seq = iter(seq)\n\n    result = []\n    old = 0\n    item = next(seq)\n    for index in sorted(n):\n        for i in range(index - old):\n            item = next(seq)\n        result.append(item)\n        old = index\n\n    order = [x[1] for x in sorted(zip(n, range(len(n))))]\n    return (result[i] for i in order)\n\n\ndef get(ind, coll, lazy=False):\n    \"\"\"\n\n    >>> get(0, 'Hello')\n    'H'\n\n    >>> get([1, 0], 'Hello')\n    ('e', 'H')\n\n    >>> get(slice(1, 4), 'Hello')\n    ('e', 'l', 'l')\n\n    >>> get(slice(1, 4), 'Hello', lazy=True)\n    <itertools.islice object at ...>\n    \"\"\"\n    if isinstance(ind, list):\n        result = nth_list(ind, coll)\n    elif isinstance(ind, slice):\n        result = islice(coll, ind.start, ind.stop, ind.step)\n    else:\n        if isinstance(coll, Iterator):\n            result = nth(ind, coll)\n        else:\n            result = coll[ind]\n    if not lazy and isinstance(result, Iterator):\n        result = tuple(result)\n    return result\n\n\ndef ndget(ind, data):\n    \"\"\"\n    Get from N-Dimensional getable\n\n    Can index with elements, lists, or slices.  Mimic's numpy fancy indexing on\n    generic indexibles.\n\n    >>> data = [[[1, 2], [3, 4]], [[5, 6], [7, 8]]]\n    >>> ndget(0, data)\n    [[1, 2], [3, 4]]\n    >>> ndget((0, 1), data)\n    [3, 4]\n    >>> ndget((0, 0, 0), data)\n    1\n    >>> ndget((slice(0, 2), [0, 1], 0), data)\n    ((1, 3), (5, 7))\n    \"\"\"\n    if isinstance(ind, tuple) and len(ind) == 1:\n        ind = ind[0]\n    if not isinstance(ind, tuple):\n        return get(ind, data)\n    result = get(ind[0], data)\n    if isinstance(ind[0], (list, slice)):\n        return type(result)(ndget(ind[1:], row) for row in result)\n    else:\n        return ndget(ind[1:], result)\n\n\ndef normalize_to_date(dt):\n    if isinstance(dt, datetime.datetime) and not dt.time():\n        return dt.date()\n    else:\n        return dt\n\n\ndef assert_allclose(lhs, rhs):\n    for tb in map(zip, lhs, rhs):\n        for left, right in tb:\n            if isinstance(left, (np.floating, float)):\n                # account for nans\n                assert np.all(np.isclose(left, right, equal_nan=True))\n                continue\n            if isinstance(left, datetime.datetime):\n                left = normalize_to_date(left)\n            if isinstance(right, datetime.datetime):\n                right = normalize_to_date(right)\n            assert left == right\n\n\ndef example(filename, datapath=os.path.join('examples', 'data')):\n    import blaze\n    return os.path.join(os.path.dirname(blaze.__file__), datapath, filename)\n\n\ndef available_memory():\n    return psutil.virtual_memory().available\n\n\ndef listpack(x):\n    \"\"\"\n    >>> listpack(1)\n    [1]\n    >>> listpack((1, 2))\n    [1, 2]\n    >>> listpack([1, 2])\n    [1, 2]\n    \"\"\"\n    if isinstance(x, tuple):\n        return list(x)\n    elif isinstance(x, list):\n        return x\n    else:\n        return [x]\n\n\n@dispatch(datetime.datetime)\ndef json_dumps(dt):\n    s = dt.isoformat()\n    if not dt.tzname():\n        s = s + 'Z'\n    return s\n", "path": "blaze/utils.py"}]}