##### SUMMARY
The `get_certificate` module should support a cryptography backend, so PyOpenSSL can be deprecated / removed eventually.

##### ISSUE TYPE
- Feature Idea

##### COMPONENT NAME
get_certificate

result = dict()
    backend = cert._backend
    x509_obj = cert._x509
    for i in range(backend._lib.X509_get_ext_count(x509_obj)):
        ext = backend._lib.X509_get_ext(x509_obj, i)
        if ext == backend._ffi.NULL:
            continue
        crit = backend._lib.X509_EXTENSION_get_critical(ext)
        data = backend._lib.X509_EXTENSION_get_data(ext)
        backend.openssl_assert(data != backend._ffi.NULL)
        der = backend._ffi.buffer(data.data, data.length)[:]
        entry = dict(
            critical=(crit == 1),
            value=base64.b64encode(der),
        )
        oid = _obj2txt(backend._lib, backend._ffi, backend._lib.X509_EXTENSION_get_object(ext))
        result[oid] = entry
    return result