docstr: Register a collation, then deregister it. Make sure an error is raised if we try
  to use it.
code: def test_deregister_collation(self):
      """
      Register a collation, then deregister it. Make sure an error is raised if we try
      to use it.
      """
      con = self.con
      con.create_collation("mycoll", lambda x, y: (x > y) - (x < y))
      con.create_collation("mycoll", None)
      with self.assertRaises(sqlite.OperationalError) as cm:
          con.execute(
              "select 'a' as x union select 'b' as x order by x collate mycoll"
          )
      self.assertEqual(
          str(cm.exception), "no such collation sequence: mycoll"
      )
  
imports: import contextlib
  import sqlite3
  import unittest
  from test.support.os_helper import TESTFN, unlink
  from .util import memory_database, cx_limit, with_tracebacks
  from .util import MemoryDatabaseMixin
label_desc: Use image node_id 8 for calling the CollationTests obj's underlying member method code with example usage: obj.test_deregister_collation() without return types