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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _module_callers(parser, modname, result):
 """Adds any calls to executables contained in the specified module. """

    if modname in result:
        #We have already processed this module.
        return
    
    module = parser.get(modname)
    mresult = {}
    if module is not None:
        for xname, xinst in module.executables():
            _exec_callers(xinst, mresult)
        result[modname] = mresult
        
        for depkey in module.dependencies:
            depmod = depkey.split('.')[0].lower()
            _module_callers(parser, depmod, result)