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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 resolve(self, symbol):
 """ Resolve a symbol using the entrypoint group. :param symbol: The symbol being resolved. :returns: The value of that symbol. If the symbol cannot be found, or if no entrypoint group was passed to the constructor, will return ``None``. """


        # Search for a corresponding symbol
        if symbol not in self._resolve_cache:
            result = None

            # Search through entrypoints only if we have a group
            if self._group is not None:
                for ep in pkg_resources.iter_entry_points(self._group, symbol):
                    try:
                        result = ep.load()
                    except (ImportError, AttributeError,
                            pkg_resources.UnknownExtra):
                        continue

                    # We found the result we were looking for
                    break

            # Cache the result
            self._resolve_cache[symbol] = result

        return self._resolve_cache[symbol]