how to resolve this probleme:

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Brokerage Error: The contract description specified for SI is ambiguous;. you must specify the multiplier or trading class.. Origin: Subscribe: SI29Z20 (FUT SI USD NYMEX) Brokerage Error: The contract description specified for SI is ambiguous;. you must specify the multiplier or trading class.. Origin: Subscribe: SI27F21 (FUT SI USD NYMEX) Brokerage Error: The contract description specified for SI is ambiguous;. you must specify the multiplier or trading class.. Origin: Subscribe: SI28U20 (FUT SI USD NYMEX) Brokerage Error: The contract description specified for SI is ambiguous;. you must specify the multiplier or trading class.. Origin: Subscribe: SI27Q20 (FUT SI USD NYMEX) Brokerage Error: The contract description specified for SI is ambiguous;. you must specify the multiplier or trading class.. Origin: Subscribe: SI28V20 (FUT SI USD NYMEX)

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