How do you retrieve the filename of a file uploaded with st.file_uploader?
If you upload a single file (i.e. accept_multiple_files=False), the filename can be retrieved by using the .name attribute on the returned UploadedFile object:
```python
import streamlit as st
uploaded_file = st.file_uploader("Upload a file")
if uploaded_file:
   st.write("Filename: ", uploaded_file.name)
```
If you upload multiple files (i.e. accept_multiple_files=True), the individual filenames can be retrieved by using the .name attribute on each UploadedFile object in the returned list:
```python
import streamlit as st
uploaded_files = st.file_uploader("Upload multiple files", accept_multiple_files=True)
if uploaded_files:
   for uploaded_file in uploaded_files:
       st.write("Filename: ", uploaded_file.name)
```
