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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 is_pinned(self):
 # type: () -> bool """Return whether I am pinned to an exact version. For example, some-package==1.2 is pinned; some-package>1.2 is not. """

        specifiers = self.specifier
        return (len(specifiers) == 1 and
                next(iter(specifiers)).operator in {'==', '==='})