converts a value to the prefixed rdf ns equivalent. If not found
            returns the value as is

        args:
            value: the value to convert

def convert_to_ns(self, value):
        ''' converts a value to the prefixed rdf ns equivalent. If not found
            returns the value as is

        args:
            value: the value to convert
        '''
        parsed = self.parse_uri(value)

        try:
            rtn_val = "%s_%s" % (self.uri_dict[parsed[0]], parsed[1])
        except KeyError:
            rtn_val = self.pyhttp(value)
        return rtn_val