input: Write a function to extract all email addresses from a given string. The function should return a list of email addresses found in the input string.
  import re
  
  def find_emails(text):
      regex = r"([a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+)"
      emails = re.findall(regex, text)
      return emails
  
  assert find_emails("This is an example with two emails: john@example.com, and jane@example.com")==["john@example.com", "jane@example.com"]
  assert find_emails("There are no emails in this text.")==[]
  assert find_emails("Email1: user@domain.com, Email2: another.user@another-domain.net")==["user@domain.com", "another.user@another-domain.net"]
  assert find_emails("")==[]
  assert find_emails("Invalid email format: @example.com")==[]
output: import re
  
  def find_emails(text):
      regex = r"([a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+)"
      emails = re.findall(regex, text)
      return emails