input: Write a function to generate a random password of 10 characters using lowercase and uppercase letters.
  assert len(generatePassword())==10
  assert all(c.isalpha() for c in generatePassword())
  assert generatePassword() != generatePassword()
output: import random
  import string
  
  def generatePassword():
      characters = string.ascii_letters
      password = ''.join(random.choice(characters) for _ in range(10))
      return password