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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 get_value_matched_by_regex(field_name, regex_matches, string):
 """Ensure value stored in regex group exists."""

    try:
        value = regex_matches.group(field_name)
        if value is not None:
            return value
    except IndexError:
        pass

    raise MissingFieldError(string, field_name)