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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 upper_camel(string, prefix='', suffix=''):
 """ Generate a camel-case identifier with the first word capitalised. Useful for class names. Takes a string, prefix, and optional suffix. `prefix` can be set to `''`, though be careful - without a prefix, the function will throw `InvalidIdentifier` when your string starts with a number. Example: 'IAmAClass' """


    return require_valid(append_underscore_if_keyword(''.join(
        upper_case_first_char(word)
        for word in en.words(' '.join([prefix, string, suffix])))
    ))