def METHOD_NAME(stmt_type: str) -> Union[None, Statement]:
    """Return INDRA statement type from ACSN relation.
    Parameters
    ----------
    stmt_type :
        An ACSN relationship type
    Returns
    -------
    :
        INDRA equivalent of the ACSN relation type or None if a mappings
        is not available.
    """
    if stmt_type in rel_mapping:
        mapped_stmt_type = rel_mapping[stmt_type]
        return mapped_stmt_type