input: Write a python function to validate email addresses.
  assert is_valid_email("test@example.com") == True
  assert is_valid_email("invalidemail@.com") == False
  assert is_valid_email("another.test@domain.co.uk") == True
  assert is_valid_email("missingatsign.com") == False
  assert is_valid_email("missingdot@com") == False
output: def is_valid_email(email):
      import re
      pattern = r'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$'
      return bool(re.match(pattern, email))