class_docstr: Test shared Alert class.
docstr: Alert Class - Compute Diff - Top Level Keys
docstr_tok: ["Alert","Class","-","Compute","Diff","-","Top","Level","Keys"]
code: def test_compute_diff_top_level(self):
      """Alert Class - Compute Diff - Top Level Keys"""
      common = {"c": 3}
      record = {"a": 1, "b": 2, "c": 3}
      assert_equal(
          {"a": 1, "b": 2}, Alert._compute_diff(common, record)
      )
  
imports: import copy
  from datetime import datetime, timedelta
  import json
  from nose.tools import assert_equal, assert_false, assert_is_instance, assert_not_in, assert_raises, assert_true
  from streamalert.shared.alert import Alert, AlertCreationError
label_desc: Use image node_id 32 for calling the TestAlert obj's underlying member method code with example usage: obj.test_compute_diff_top_level() without return types