[REQUEST] support print call graph of current function

[leiyang]

it seems rich only raise the call graph when an exception triggered, the output is great
can we support print the call graph of this function with rich ? something like

def f(x):
    print(''.join(traceback.format_stack()))

I want to get who called, f(x) and the caller's caller (call graph)
and the callgraph could be stored in a variable, I could print it myself