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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_module_paths(execd_dir=None):
 """Generate a list of full paths to modules within execd_dir."""

    if not execd_dir:
        execd_dir = default_execd_dir()

    if not os.path.exists(execd_dir):
        return

    for subpath in os.listdir(execd_dir):
        module = os.path.join(execd_dir, subpath)
        if os.path.isdir(module):
            yield module