http://www.elasticsearch.org/guide/reference/query-dsl/numeric-range-filter.html
        Filters documents with fields that have values within a certain numeric range. Similar to range filter, except that it works only with numeric values, and the filter execution works differently.

def numeric_range(cls, field, from_value, to_value, include_lower=None, include_upper=None):
        '''
        http://www.elasticsearch.org/guide/reference/query-dsl/numeric-range-filter.html
        Filters documents with fields that have values within a certain numeric range. Similar to range filter, except that it works only with numeric values, and the filter execution works differently.
        '''
        instance = cls(numeric_range={field: {'from': from_value, 'to': to_value}})
        if include_lower is not None:
            instance['numeric_range'][field]['include_lower'] = include_lower
        if include_upper is not None:
            instance['numeric_range'][field]['include_upper'] = include_upper
        return instance