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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 find_greeting(s):
 """ Return the the greeting string Hi, Hello, or Yo if it occurs at the beginning of a string 'Hi' 'Hello' 'Yo' 'Hello' None None """

    if s[0] == 'H':
        if s[:3] in ['Hi', 'Hi ', 'Hi,', 'Hi!']:
            return s[:2]
        elif s[:6] in ['Hello', 'Hello ', 'Hello,', 'Hello!']:
            return s[:5]
    elif s[0] == 'Y':
        if s[1] == 'o' and s[:3] in ['Yo', 'Yo,', 'Yo ', 'Yo!']:
            return s[:2]
    return None