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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 execd_submodule_paths(command, execd_dir=None):
 """Generate a list of full paths to the specified command within exec_dir. """

    for module_path in execd_module_paths(execd_dir):
        path = os.path.join(module_path, command)
        if os.access(path, os.X_OK) and os.path.isfile(path):
            yield path