code: public static int getNumInputs(final Class<? extends Operator<?>> contractType) {
  
  		if (GenericDataSourceBase.class.isAssignableFrom(contractType)) {
  			return 0;
  		}
  		if (GenericDataSinkBase.class.isAssignableFrom(contractType)
  			|| SingleInputOperator.class.isAssignableFrom(contractType)) {
  			return 1;
  		}
  		if (DualInputOperator.class.isAssignableFrom(contractType)) {
  			return 2;
  		}
  		throw new IllegalArgumentException("not supported");
  	}
docs: Returns the number of inputs for the given {@link Operator} type.<br>
  Currently, it can be 0, 1, or 2.
  
  @param contractType
  the type of the Operator
  @return the number of input contracts