input: Write a python function to validate an email address using regular expressions.
  assert validate_email("test@example.com") == True
  assert validate_email("invalid-email") == False
  assert validate_email("user.name+tag+sorting@example.com") == True
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