docs: public TypeInformation<T> getType() {
  		if (type instanceof MissingTypeInfo) {
  			MissingTypeInfo typeInfo = (MissingTypeInfo) type;
  			throw new InvalidTypesException("The return type of function '" + typeInfo.getFunctionName()
  					+ "' could not be determined automatically, due to type erasure. "
  					+ "You can give type information hints by using the returns(...) method on the result of "
  					+ "the transformation call, or by letting your function implement the 'ResultTypeQueryable' "
  					+ "interface.", typeInfo.getTypeException());
  		}
  		typeUsed = true;
  		return this.type;
  	}