def METHOD_NAME(self, field_name):
    """Apply keyword searches."""
    if field_name.startswith("^"):
        return "%s__istartswith" % field_name[1:]
    elif field_name.startswith("="):
        return "%s__iexact" % field_name[1:]
    elif field_name.startswith("@"):
        return "%s__search" % field_name[1:]
    else:
        return "%s__icontains" % field_name