input: Write a function to validate email addresses using the given regex pattern.
  assert validate_email("example@example.com") == True
  assert validate_email("user.name@domain.co") == True
  assert validate_email("user@domaincom") == False
  assert validate_email("user@.com") == False
output: def validate_email(email):
      import re
      pattern = r'^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+$'
      return re.match(pattern, email) is not None