def _check_src_type(filters):
    """Check whether src_type is in filters and set custom warning."""
    if 'src_type' not in filters:
        filters['src_type'] = None
    warn_text = (
        'The spatial filter does not contain src_type and a robust guess of src_type is not possible without src. Consider recomputing the filter.'
        )
    return filters, warn_text
