<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def value(self, raw_value):
 """Decode param as decimal value."""

        try:
            return decimal.Decimal(raw_value)
        except decimal.InvalidOperation:
            raise ValueError(
                "Could not parse '{}' value as decimal".format(raw_value)
            )