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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 validate_instance_username(self, username):
        ''' Validate instance username '''
        # 1-16 alphanumeric characters - first character must be a letter -
        # cannot be a reserved MySQL word
        if re.match('[\w-]+$', username) is not None:
            if len(username) <= 16 and len(username) >= 1:
                if username[0].isalpha():
                    if username not in MYSQL_RESERVED_WORDS:
                        return True
        return '*** Error: Usernames must be 1-16 alphanumeric chracters, \
            first a letter, cannot be reserved MySQL word.'