def get_transaction_type_from_symbol(transaction_type)
      begin
        target_type = transaction_type.to_s.upcase
        return if target_type.empty?
        self.class.const_get(target_type)
      rescue NameError => error
        raise Bitpagos::Errors::InvalidTransactionType.new(error.message)
      end
    end
def get_transaction_type_from_symbol(transaction_type)
      begin
        target_type = transaction_type.to_s.upcase
        return if target_type.empty?
        self.class.const_get(target_type)
      rescue NameError => error
        raise Bitpagos::Errors::InvalidTransactionType.new(error.message)
      end
    end
Takes a symbol and returns the proper transaction type.

 @param [Symbol] Can be :pending, :waiting, :completed or :partially_paid
 @return [String,nil] Returns the corresponding "PE", "WA", "CO" or "PP"