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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 element_text_should_be(self, locator, expected, message=''):

 """Verifies element identified by ``locator`` exactly contains text ``expected``.
 
 In contrast to `Element Should Contain Text`, this keyword does not try
 a substring match but an exact match on the element identified by ``locator``.
 
 ``message`` can be used to override the default error message.
 
 New in AppiumLibrary 1.4.
 """

        self._info("Verifying element '%s' contains exactly text '%s'."
                    % (locator, expected))
        element = self._element_find(locator, True, True)
        actual = element.text
        if expected != actual:
            if not message:
                message = "The text of element '%s' should have been '%s' but "\
                          "in fact it was '%s'." % (locator, expected, actual)
            raise AssertionError(message)