Add unit test for ui (#1265)

<!-- Contributing guide:
https://github.com/openvinotoolkit/datumaro/blob/develop/CONTRIBUTING.md
-->

### Summary

<!--
Resolves #111 and #222.
Depends on #1000 (for series of dependent commits).

This PR introduces this capability to make the project better in this
and that.

- Added this feature
- Removed that feature
- Fixed the problem #1234
-->

Added unit test for gui

### How to test
<!-- Describe the testing procedure for reviewers, if changes are
not fully covered by unit tests or manual testing can be complicated.
-->

### Checklist
<!-- Put an 'x' in all the boxes that apply -->
- [X] I have added unit tests to cover my changes.​
- [ ] I have added integration tests to cover my changes.​
- [ ] I have added the description of my changes into
[CHANGELOG](https://github.com/openvinotoolkit/datumaro/blob/develop/CHANGELOG.md).​
- [ ] I have updated the
[documentation](https://github.com/openvinotoolkit/datumaro/tree/develop/docs)
accordingly

### License

- [ ] I submit _my code changes_ under the same [MIT
License](https://github.com/openvinotoolkit/datumaro/blob/develop/LICENSE)
that covers the project.
  Feel free to contact the maintainers if that's a concern.
- [ ] I have updated the license header for each file (see an example
below).

```python
# Copyright (C) 2023 Intel Corporation
#
# SPDX-License-Identifier: MIT
```

gui/ABOUTUS.md

@@ -1,7 +1,5 @@
 # Who We Are?
 
-
-
 ## Contributing
 
 [(Back to top)](#dataset-management-framework-datumaro)

gui/datumaro_gui/apps/__init__.py

@@ -1,2 +1,2 @@
-from .home import main as home
 from .aboutus import main as aboutus
+from .home import main as home

gui/datumaro_gui/apps/aboutus.py

@@ -1,10 +1,10 @@
-import streamlit as st
-
 from pathlib import Path
 
+import streamlit as st
+
 
 def main():
-    st.markdown((Path(__file__).parents[2]/"ABOUTUS.md").read_text())
+    st.markdown((Path(__file__).parents[2] / "ABOUTUS.md").read_text())
 
 
 if __name__ == "__main__":

gui/datumaro_gui/apps/home.py

@@ -1,10 +1,10 @@
-import streamlit as st
-
 from pathlib import Path
 
+import streamlit as st
+
 
 def main():
-    st.markdown((Path(__file__).parents[2]/"README.md").read_text())
+    st.markdown((Path(__file__).parents[2] / "README.md").read_text())
 
 
 if __name__ == "__main__":

gui/datumaro_gui/components/multiple/tabs/compare.py

@@ -93,7 +93,7 @@ def main():
                 "datasets.\n\nBy the way, the low-level analysis takes a bit of time to compute. Please bear with us "
                 "for a moment; your patience is much appreciated!",
             )
-            on = st.toggle("Show low-level table", key="low_lvl_tb_toggle")
+            on = st.toggle("Show low-level table", key="tg_low_lvl_on_comp_mul")
             if on:
                 if low_level_df is None:
                     _, _, low_level_table, _ = comparator.compare_datasets(
@@ -155,7 +155,12 @@ def normalize_string(s):
                     return s
 
                 threshold = st.slider(
-                    "Desired similarity threshold", 0.0, 1.0, 0.7, step=0.1, key="sim_slider"
+                    "Desired similarity threshold",
+                    0.0,
+                    1.0,
+                    0.7,
+                    step=0.1,
+                    key="sd_threshold_comp_mul",
                 )
                 # Iterate over items in the first list
                 for item1 in unmatches[uploaded_file_1]:
@@ -206,7 +211,7 @@ def normalize_string(s):
                 )
 
                 if (
-                    st.button("Finalize mapping", key="mapping_btn")
+                    st.button("Finalize mapping", key="btn_mapping_comp_mul")
                     and grid_table["selected_rows"] is not None
                 ):
                     sel_row = grid_table["selected_rows"]

gui/datumaro_gui/components/multiple/tabs/export.py

@@ -74,7 +74,7 @@ def main():
                 key="ti_path_export_mult",
             )
 
-        export_btn = st.button("Export", "btn_export_mult")
+        export_btn = st.button("Export", key="btn_export_mult")
         if export_btn:
             data_helper = dataset_dict.get(selected_dataset, None)
             data_helper.export(selected_path, format=selected_format, save_media=True)