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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 from_string(cls, address, case_sensitive=False):
 """Alternate constructor for building from a string. :param str address: An email address in <user>@<domain> form :param bool case_sensitive: passed directly to the constructor argument of the same name. :returns: An account from the given arguments :rtype: :class:`Account` """

        assert isinstance(address, str), 'address must be str'
        username, domainname = address.split('@')
        return cls(username, domainname, case_sensitive=case_sensitive)