<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def brain_post(connection, requirements=None):
 """ Power On Self Test for the brain. Checks that the brain is appropriately seeded and ready for use. Raises AssertionError's if the brain is not ready. :param connection: <rethinkdb.net.DefaultConnection> :param requirements:<dict> keys=Required Databases, key-values=Required Tables in each database :return: <rethinkdb.net.DefaultConnection> if verified """

    assert isinstance(connection, DefaultConnection)
    remote_dbs = validate_get_dbs(connection)
    assert validate_brain_requirements(connection, remote_dbs, requirements)
    assert validate_write_access(connection)
    return connection