Example:

import gradio as gr

def dummy(a, b):
    return '{0} {1}'.format(a, b)

with gr.Blocks() as demo:
    a = 'Hello '
    txt = gr.Textbox(value="test", label="Query", lines=1)
    answer = gr.Textbox(value="", label="Answer")
    btn = gr.Button(value="Submit")
    btn.click(dummy, inputs=[txt], outputs=[answer])
    gr.ClearButton([answer])

demo.launch()

How can I change btn.click so that it passes the variable a to dummy()?