Implementar um Card com shadow

```python
from Tkinter import *
top = Tk()
top['bg'] = '#f5f5f5'

import urllib
image = urllib.urlopen('https://raw.githubusercontent.com/ankitaggarwal011/PyCNN/master/images/lenna.gif').read()

DEFAULT_COLORS = ['#f0f0f0', '#ebebeb', '#e3e3e3', '#d4d4d4']
class GradientFrame(Frame):
def __init__(self, parent, colors=DEFAULT_COLORS, pad=1):
Frame.__init__(self, parent)

self.frames = []
last = self
self.configure(bg=parent['bg'])

for i in colors:
frame = Frame(last, bg=i)
frame.grid(pady=pad, padx=pad)
self.frames.append(frame)
last = frame

self.content_frame = last
self.content_frame.configure(bg='white')

fr = GradientFrame(top, pad=2)
fr.pack(pady=50, padx=50, expand='yes')

photo = PhotoImage(data=image)
label = Label(fr.content_frame, image=photo).grid(row=0, column=0)

Label(fr.content_frame, text='Card', bg='white').grid(sticky='w',
row=1, column=0, pady=20, padx=20)

top.mainloop()
```


The issue names no project file, test, or entry point; start by locating the existing Tkinter UI implementation and compare it with the supplied GradientFrame example. Done means the library provides the requested card with a shadow appearance, but the issue gives no acceptance test or precise integration location.

Written by the indexing model from the issue text.