code: func ParseStatement(input string) (Statement, error) {
  	stmts, _, err := ParseStatements("", input)
  	if err != nil {
  		return nil, err
  	}
  	if len(stmts) != 1 {
  		return nil, fmt.Errorf("expected exactly one statement")
  	}
  	return stmts[0], nil
  }
docs: // ParseStatement returns exactly one statement.
  // A statement might be a term, expression, rule, etc. Regardless,
  // this function expects *exactly* one statement. If multiple
  // statements are parsed, an error is returned.