Queries /<security_type> endpoint to return a paged
        list of securities.

def get_securities(self, page=1, **filter_param):
        """
        Queries /<security_type> endpoint to return a paged
        list of securities.
        """
        url_path = self._build_url_path(None, None)
        params = {'page': page}
        # the endpoints respond just fine to invaliid query params,
        # they just ignore them, but the the real value of the endpoints
        # is only revealed when using the filters, so let's not waste
        # requests on filters that don't do anything.
        if filter_param:
            query_filter = filter_param.popitem()
            if query_filter[0] in self.VALID_SECURITY_FILTERS:
                params[query_filter[0]] = query_filter[1]
            else:
                error_msg = 'Invalid filter param. Must be one of: {0}'.format(','.join(self.VALID_SECURITY_FILTERS))
                raise exceptions.PyChartsRequestException(error_msg)

        return self._get_data(url_path, params)