Refactor the following code. Add typehints and format according to PEP8. Code: import ctypes
import math
import re
import tkinter as tk
from tkinter import font as tkFont, ttk

# --- Conversion Functions ---

def kg_to_lb(kg):
    """Convert kilograms to pounds."""
    return kg / 0.45359237

def lb_to_kg(lb):
    """Convert pounds to kilograms."""
    return lb * 0.45359237

# --- Evaluation Function ---

def evaluate_expression(expression, use_degrees=False):
    """Safely evaluate a mathematical expression considering degree mode."""
    def convert_angle(func, x):
        return func(math.radians(x)) if use_degrees else func(x)

    def inverse_convert_angle(func, x):
        result = func(x)
        return math.degrees(result) if use_degrees else result

    safe_functions = {
        'sqrt': math.sqrt,
        'sin': lambda x: convert_angle(math.sin, x),
        'cos': lambda x: convert_angle(math.cos, x),
        'tan': lambda x: convert_angle(math.tan, x),
        'asin': lambda x: inverse_convert_angle(math.asin, x),
        'acos': lambda x: inverse_convert_angle(math.acos, x),
        'atan': lambda x: inverse_convert_angle(math.atan, x),
        'log': math.log10,
        'ln': math.log,
        'pi': math.pi,
        'e': math.e,
        'lb': kg_to_lb,
        'kg': lb_to_kg
    }

    expression = expression.replace('^', '**')
    func_calls = re.findall(r'(\b\w+\b)\(([^)]+)\)', expression)

    for func, arg in func_calls:
        if func in ['asin', 'acos']:
            try:
                value = eval(arg, {"__builtins__": None}, safe_functions)
                if not -1 <= value <= 1:
                    raise ValueError(f"{func}(x) is undefined for |x| > 1")
            except Exception as e:
                return f"Error: {e}"

    try:
        result = eval(expression, {"__builtins__": None}, safe_functions)
        if isinstance(result, float) and abs(result) < 1e-10:
            result = 0.0
        return round(result, 2) if isinstance(result, (int, float)) else result
    except Exception as e:
        return f"Error: {e}"

# --- Calculator GUI Class ---

class CalculatorGUI:
    """Tkinter-based Calculator with Degrees/Radians toggle and history."""
    
    def __init__(self, master):
        self.master = master
        self.use_degrees = tk.BooleanVar(value=False)
        self.set_dpi_awareness()
        self.setup_window()
        self.create_widgets()
        self.layout_widgets()
        self.configure_grid()

    def set_dpi_awareness(self):
        """Enable high-DPI support on Windows."""
        try:
            ctypes.windll.shcore.SetProcessDpiAwareness(1)
        except:
            pass

    def setup_window(self):
        """Configure the main application window."""
        self.master.title("Calculator")
        self.master.geometry("1200x720")

    def create_widgets(self):
        """Initialize all GUI components."""
        self.font = tkFont.Font(family="Roboto Flex", size=16)
        self.expression_var = tk.StringVar()
        self.entry = ttk.Entry(self.master, textvariable=self.expression_var, font=self.font, width=50)
        self.entry.bind("<Return>", self.calculate)
        self.history_text = tk.Text(self.master, width=70, height=10, font=self.font, wrap="none", state=tk.DISABLED)
        self.scrollbar = ttk.Scrollbar(self.master, orient="vertical", command=self.history_text.yview)
        self.history_text.configure(yscrollcommand=self.scrollbar.set)
        self.create_toggle_button()
        supported_info = (
            "Functions: sqrt, sin, cos, tan, asin, acos, atan, log, ln\n"
            "Constants: pi, e\n"
            "Conversions: lb(kg), kg(lb)"
        )
        self.supported_label = ttk.Label(self.master, text=supported_info, font=self.font)

    def create_toggle_button(self):
        """Create the Degrees/Radians toggle button."""
        style = ttk.Style()
        style.configure('ToggleButton.TButton', font=self.font, padding=0)
        self.mode_button = ttk.Button(
            self.master,
            text="Radians",
            command=self.toggle_mode,
            style='ToggleButton.TButton'
        )

    def layout_widgets(self):
        """Arrange widgets within the window."""
        self.entry.grid(row=0, column=0, columnspan=2, padx=5, pady=5, sticky="ew")
        self.history_text.grid(row=1, column=0, padx=5, pady=5, sticky="nsew")
        self.scrollbar.grid(row=1, column=1, padx=(0,5), pady=5, sticky="ns")
        self.mode_button.grid(row=2, column=0, columnspan=2, padx=5, pady=5, sticky="w")
        self.supported_label.grid(row=3, column=0, columnspan=2, padx=5, pady=10, sticky="w")

    def configure_grid(self):
        """Make the grid layout responsive."""
        self.master.columnconfigure(0, weight=1)
        self.master.columnconfigure(1, weight=0)
        self.master.rowconfigure(1, weight=1)

    def toggle_mode(self):
        """Switch between Degrees and Radians modes."""
        if self.use_degrees.get():
            self.use_degrees.set(False)
            self.mode_button.config(text="Radians")
        else:
            self.use_degrees.set(True)
            self.mode_button.config(text="Degrees")

    def calculate(self, event=None):
        """Evaluate the expression and update history."""
        expression = self.expression_var.get().strip()
        if not expression:
            return
        result = evaluate_expression(expression, use_degrees=self.use_degrees.get())
        self.display_result(expression, result)
        self.expression_var.set("")

    def display_result(self, expression, result):
        """Append the calculation to the history log."""
        self.history_text.config(state=tk.NORMAL)
        mode = "Degrees" if self.use_degrees.get() else "Radians"
        self.history_text.insert(tk.END, f"[{mode}] {expression} = {result}\n")
        self.history_text.config(state=tk.DISABLED)
        self.history_text.see(tk.END)

# --- Main Function ---

def main():
    """Run the Calculator application."""
    root = tk.Tk()
    CalculatorGUI(root)
    root.mainloop()

if __name__ == "__main__":
    main()