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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 unicode_left(s, width):
 """Cut unicode string from left to fit a given width."""

    i = 0
    j = 0
    for ch in s:
        j += __unicode_width_mapping[east_asian_width(ch)]
        if width < j:
            break
        i += 1
    return s[:i]