def _normalize_validate(validate):
    """
    Coerces the validate attribute on a Marshmallow field to a consistent type.

    The validate attribute on a Marshmallow field can either be a single
    Validator or a collection of Validators.

    :param Validator|list[Validator] validate:
    :rtype: list[Validator]
    """
    if callable(validate):
        return [validate]
    else:
        return validate