docstr: Test streamlit.string_util.simplify_number.
code: def test_simplify_number(self):
      """Test streamlit.string_util.simplify_number."""
  
      self.assertEqual(string_util.simplify_number(100), "100")
  
      self.assertEqual(string_util.simplify_number(10000), "10k")
  
      self.assertEqual(string_util.simplify_number(1000000), "1m")
  
      self.assertEqual(string_util.simplify_number(1000000000), "1b")
  
      self.assertEqual(string_util.simplify_number(1000000000000), "1t")
  
file_path: streamlit/lib/tests/streamlit/string_util_test.py
imports: import unittest
  from parameterized import parameterized
  from streamlit import string_util
label_desc: Use image node_id 4 for calling the StringUtilTest obj's underlying member method code with example usage: obj.test_simplify_number() without return types