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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 _n(name):
 """Return valid PySB name."""

    n = name.encode('ascii', errors='ignore').decode('ascii')
    n = re.sub('[^A-Za-z0-9_]', '_', n)
    n = re.sub(r'(^[0-9].*)', r'p\1', n)
    return n