def xpath_eval(self,expr):
ctxt = common_doc.xpathNewContext()<EOL>ctxt.setContextNode(self.xmlnode)<EOL>ctxt.xpathRegisterNs("<STR_LIT>",self.ns.getContent())<EOL>ret=ctxt.xpathEval(to_utf8(expr))<EOL>ctxt.xpathFreeContext()<EOL>return ret<EOL>
Evaluate XPath expression in context of `self.xmlnode`.

:Parameters:
    - `expr`: the XPath expression
:Types:
    - `expr`: `unicode`

:return: the result of the expression evaluation.
:returntype: list of `libxml2.xmlNode`