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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _get_sqla_coltype_class_from_str(coltype: str, dialect: Dialect) -> Type[TypeEngine]: """ Returns the SQLAlchemy class corresponding to a particular SQL column type in a given dialect. Performs an upper- and lower-case search. For example, the SQLite dialect uses upper case, and the MySQL dialect uses lower case. """

    # noinspection PyUnresolvedReferences
    ischema_names = dialect.ischema_names
    try:
        return ischema_names[coltype.upper()]
    except KeyError:
        return ischema_names[coltype.lower()]