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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 verify_sigfile(sigdir, sig):
 """Verify a signature file"""

    cmd = ['sigtool', '-i', '%s/%s.cvd' % (sigdir, sig)]
    sigtool = Popen(cmd, stdout=PIPE, stderr=PIPE)
    ret_val = sigtool.wait()
    return ret_val == 0