plpython: sys module doesn't know about _getframe

Steven D. Arnold (stevena(at)neosynapse(dot)net) reports a bug with a severity of 3
The lower the number the more severe it is.

Short Description
plpython: sys module doesn't know about _getframe

Long Description
I have a module which I import and use in plpython functions. One function in this module imports sys and then uses sys._getframe(). When it tries to do this, plpython says:

exceptions.AttributeError: 'sys' module has no attribute '_getframe'

The same function using Python directly works fine. Does plpython use a specialized version of Python or a specialized sys module?

Sample Code
create function foo() returns integer as '
import data_handler
result = data_handler.qse("""SELECT * FROM users""")
return 1
' language 'plpython';

[In module data_handler]
import sys
def qse(s, layers=1):
loc = sys._getframe(layers).f_locals
glb = sys._getframe(layers).f_globals
[...]
return s

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