text: Title: Improve existing unit tests
  Body: * Improve efficiency:  Many of the existing unit tests (in cleanlab/tests/) can be made more efficient without fundamentally changing the quality of the test.  We recommend timing the unit tests to identify which ones take the longest and focusing on those.  Usually these will be tests that rely on some toy dataset. One way to speed such tests up is to reduce the size of the dataset, but be careful that the test remains useful and still checks for the key properties it is assessing!
  
  *  Improve quality of checks:  Some of the existing unit tests only verify certain code runs properly. These tests can be improved to verify the outputs from the code match the expected outputs (both in terms of object characteristics like array shape or Python type, as well as the values themselves).