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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 is_program_installed(basename):

 """
 Return program absolute path if installed in PATH.
 
 Otherwise, return None
 """

    for path in os.environ["PATH"].split(os.pathsep):
        abspath = osp.join(path, basename)
        if osp.isfile(abspath):
            return abspath