raise error when uploaded a file with more than one seq

Domain2GO.py

@@ -53,6 +53,8 @@ with st.sidebar:
                 protein_input_stringio = StringIO(bytes_data.decode("utf-16"))
                 
             fasta_sequences = SeqIO.parse(protein_input_stringio, 'fasta')
+            if len(list(fasta_sequences)) > 1:
+                st.error('Please upload a file containing only one sequence.')
             for fasta in fasta_sequences:
                 st.session_state['name'], st.session_state['sequence'] = fasta.id, str(fasta.seq)