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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 find_string(regex, s):
 """Find a string using a given regular expression. If the string cannot be found, returns None. The regex should contain one matching group, as only the result of the first group is returned. s - The string to search. regex - A string containing the regular expression. Returns a unicode string or None. """

    m = re.search(regex, s)
    if m is None:
        return None
    return m.groups()[0]