'Process the tag to get the value.
:param element: the parent element
:param tag_name: the tag name
:returns: nodeValue(can be None)'

@staticmethod
def _process_tag(element, tag_name):

    node_value = None
    try:
        processed_element = element.getElementsByTagName(tag_name)[0]
        node_value = processed_element.childNodes[0].nodeValue
        if node_value:
            node_value = node_value.strip()
    except IndexError:
        pass
    return node_value
