'Extract a given meta content form document.
Example metaNames:
"meta[name=description]"
"meta[name=keywords]"
"meta[property=og:type]"'

def get_meta_content(self, doc, metaname):

    meta = self.parser.css_select(doc, metaname)
    content = None
    if ((meta is not None) and (len(meta) > 0)):
        content = self.parser.getAttribute(meta[0], 'content')
    if content:
        return content.strip()
    return ''
