code: def from_string(cls, address, case_sensitive=False):
          
          assert isinstance(address, str), 'address must be str'
          username, domainname = address.split('@')
          return cls(username, domainname, case_sensitive=case_sensitive)
docs: 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`