'Finds a subnode in the host node and the retrieves a value from it.
@return An attribute value'

def get_text_from_subnode(self, subnode_xpath_expr):

    sub_node = self.node.find(subnode_xpath_expr)
    if (sub_node is not None):
        if (sub_node.text is not None):
            return sub_node.text
    return ''
