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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 get_bin_dir(self, build_module: str) -> str: """Return a path to the binaries dir for a build module dir. Create sub-tree of missing dirs as needed, and return full path to innermost directory. """

        bin_dir = os.path.join(self.conf.get_bin_path(), build_module)
        if not os.path.isdir(bin_dir):
            # exist_ok=True in case of concurrent creation of the same dir
            os.makedirs(bin_dir, exist_ok=True)
        return bin_dir