extensions-builtin/sd-webui-controlnet/scripts/controlnet_ui/tool_button.py

import gradio as gr

class ToolButton(gr.Button, gr.components.FormComponent):
    """Small button with single emoji as text, fits inside gradio forms"""

    def __init__(self, **kwargs):
        super().__init__(variant="tool", 
                         elem_classes=kwargs.pop('elem_classes', []) + ["cnet-toolbutton"], 
                         **kwargs)

    def get_block_name(self):
        return "button"