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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def htmlCtxtReadFd(self, fd, URL, encoding, options):
 """parse an XML from a file descriptor and build a tree. This reuses the existing @ctxt parser context """

        ret = libxml2mod.htmlCtxtReadFd(self._o, fd, URL, encoding, options)
        if ret is None:raise treeError('htmlCtxtReadFd() failed')
        __tmp = xmlDoc(_obj=ret)
        return __tmp