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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 capitalize(string):
 """Capitalize a sentence. Parameters string : `str` String to capitalize. Returns ------- `str` Capitalized string. Examples -------- 'Word word word' """

    if not string:
        return string
    if len(string) == 1:
        return string.upper()
    return string[0].upper() + string[1:].lower()