docstr: get_url raises if it gets a bad file_id.
docstr_tok: ["get_url","raises","if","it","gets","a","bad","file_id","."]
code: def test_get_url_invalid_fileid(self):
      """get_url raises if it gets a bad file_id."""
      with self.assertRaises(MediaFileStorageError):
          self.storage.get_url("not_a_file_id")
  
imports: import unittest
  from unittest import mock
  from unittest.mock import MagicMock, mock_open
  from parameterized import parameterized
  from streamlit.runtime.media_file_storage import MediaFileKind, MediaFileStorageError
  from streamlit.runtime.memory_media_file_storage import MemoryFile, MemoryMediaFileStorage, get_extension_for_mimetype
label_desc: Use image node_id 7 for calling the MemoryMediaFileStorageTest obj's underlying member method code with example usage: obj.test_get_url_invalid_fileid() without return types