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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 _string_replace(arg, pattern, replacement):
 """ Replaces each exactly occurrence of pattern with given replacement string. Like Python built-in str.replace Parameters pattern : string replacement : string Examples -------- Returns ------- replaced : string """

    return ops.StringReplace(arg, pattern, replacement).to_expr()