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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 _check_ddl_statements(value):
 """Validate DDL Statements used to define database schema. See https://cloud.google.com/spanner/docs/data-definition-language :type value: list of string :param value: DDL statements, excluding the 'CREATE DATABSE' statement :rtype: tuple :returns: tuple of validated DDL statement strings. :raises ValueError: if elements in ``value`` are not strings, or if ``value`` contains a ``CREATE DATABASE`` statement. """

    if not all(isinstance(line, six.string_types) for line in value):
        raise ValueError("Pass a list of strings")

    if any("create database" in line.lower() for line in value):
        raise ValueError("Do not pass a 'CREATE DATABASE' statement")

    return tuple(value)