我正试图在google colab上导入_udunits2。我已经设法通过康达安装了它。但是，成功安装后，当我尝试导入包时，它返回以下错误消息：

ImportError                               Traceback (most recent call last)
<ipython-input-40-f9eb376cf338> in <module>()
----> 1 from cf_units import _udunits2

/usr/local/lib/python3.6/site-packages/cf_units/__init__.py in <module>()
     43 from .util import _OrderedHashable, approx_equal
     44 
---> 45 from cf_units import _udunits2 as _ud
     46 from cf_units._udunits2 import (UT_ASCII, UT_ISO_8859_1, UT_LATIN1, UT_UTF8,
     47                                 UT_NAMES, UT_DEFINITION)

ImportError: cannot import name '_udunits2' from 'cf_units' (/usr/local/lib/python3.6/site-packages/cf_units/__init__.py)

有人对如何导入这个包有什么想法吗？