input: Write a python function to create a BankAccount class with methods to show balance, deposit, and withdraw, ensuring proper functionality.
  ```python
  class BankAccount:
      def __init__(self, username, balance):
          self.username = username
          self.balance = balance
  
      def show_balance(self):
          return f"Balance of {self.username}'s account is {self.balance}"
      
      def deposit(self, amount):
          if amount > 0:
              self.balance += amount
              return f"{amount} was added to the balance. Current balance is {self.balance}"
          else:
              return "Cannot deposit negative value"
      
      def withdraw(self, amount):
          if amount > 0:
              if amount <= self.balance:
                  self.balance -= amount
                  return f"{amount} was withdrawn from the balance. Current balance is {self.balance}"
              else:
                  return "Cannot withdraw more than current balance"
          else:
              return "Cannot withdraw negative value"
  
  # Test Cases
  account = BankAccount("JohnDoe", 100)
  assert account.show_balance() == "Balance of JohnDoe's account is 100"
  assert account.deposit(50) == "50 was added to the balance. Current balance is 150"
  assert account.withdraw(30) == "30 was withdrawn from the balance. Current balance is 120"
  assert account.deposit(-20) == "Cannot deposit negative value"
  assert account.withdraw(200) == "Cannot withdraw more than current balance"
  assert account.withdraw(-10) == "Cannot withdraw negative value"
output: class BankAccount:
      def __init__(self, username, balance):
          self.username = username
          self.balance = balance
  
      def show_balance(self):
          return f"Balance of {self.username}'s account is {self.balance}"
      
      def deposit(self, amount):
          if amount > 0:
              self.balance += amount
              return f"{amount} was added to the balance. Current balance is {self.balance}"
          else:
              return "Cannot deposit negative value"
      
      def withdraw(self, amount):
          if amount > 0:
              if amount <= self.balance:
                  self.balance -= amount
                  return f"{amount} was withdrawn from the balance. Current balance is {self.balance}"
              else:
                  return "Cannot withdraw more than current balance"
          else:
              return "Cannot withdraw negative value"
  
  # Test Cases
  account = BankAccount("JohnDoe", 100)
  assert account.show_balance() == "Balance of JohnDoe's account is 100"
  assert account.deposit(50) == "50 was added to the balance. Current balance is 150"
  assert account.withdraw(30) == "30 was withdrawn from the balance. Current balance is 120"
  assert account.deposit(-20) == "Cannot deposit negative value"
  assert account.withdraw(200) == "Cannot withdraw more than current balance"
  assert account.withdraw(-10) == "Cannot withdraw negative value"