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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 _build_backend():
 """Find and load the build backend"""

    ep = os.environ['PEP517_BUILD_BACKEND']
    mod_path, _, obj_path = ep.partition(':')
    try:
        obj = import_module(mod_path)
    except ImportError:
        raise BackendUnavailable
    if obj_path:
        for path_part in obj_path.split('.'):
            obj = getattr(obj, path_part)
    return obj