def address_to_oa_address(btc_address)
      begin
        btc_hex = decode_base58(btc_address)
        btc_hex = '0' +btc_hex if btc_hex.size==47
        address = btc_hex[0..-9] # bitcoin address without checksum
        named_addr = OA_NAMESPACE.to_s(16) + address
        oa_checksum = checksum(named_addr)
        encode_base58(named_addr + oa_checksum)
      rescue ArgumentError
        nil # bech32 format fails to decode. TODO define OA address for segwit
      end
    end
def address_to_oa_address(btc_address)
      begin
        btc_hex = decode_base58(btc_address)
        btc_hex = '0' +btc_hex if btc_hex.size==47
        address = btc_hex[0..-9] # bitcoin address without checksum
        named_addr = OA_NAMESPACE.to_s(16) + address
        oa_checksum = checksum(named_addr)
        encode_base58(named_addr + oa_checksum)
      rescue ArgumentError
        nil # bech32 format fails to decode. TODO define OA address for segwit
      end
    end
convert bitcoin address to open assets address
 @param [String] btc_address The Bitcoin address.
 @return [String] The Open Assets Address.