code: def _filter_by_range_schema(self, qs, lookup, sublookup, value, schema):
          
          # This code was written with a single use case in mind. That use case
          # required searching for objects whose ranges *intersect* with given
          # one. I did not invest time in supporting other use cases (such as
          # checking whether the ranges are exactly the same or how they are
          # different). However, such lookups *can* be added later without
          # breaking existing client code. Patches are welcome.
          sublookup = sublookup or RANGE_INTERSECTION_LOOKUP
          if not sublookup == RANGE_INTERSECTION_LOOKUP:
              raise ValueError('Range schema only supports lookup "%s".' %
                               RANGE_INTERSECTION_LOOKUP)
          try:
              _, _ = value
          except ValueError:
              raise ValueError('Range schema value must be a tuple of min and '
                               'max values; one of them may be None.')
          except TypeError:
              raise TypeError('Expected a two-tuple, got "%s"' % value)
  
          value_lookups = zip((
              'attrs__value_range_max__gte',
              'attrs__value_range_min__lte',
          ), value)
          conditions = dict((k,v) for k,v in value_lookups if v is not None)
          conditions.update({
              'attrs__schema': schema,
          })
          return conditions
docs: Filters given entity queryset by an attribute which is linked to given
          range schema. Lookups `between` yields items that lie not completely
          within given range but have intersection with it. For example, and item
          with x=(2,5) will match q=(3,None) or q=(0,3). See tests for details.
  
              qs.filter(weight_range__overlaps=(1,3))
              qs.filter(weight_range__overlaps=(1,None))