input: Write a function to extract all public email addresses from a given string using regular expression. The function should return a list of all found email addresses. If no email addresses are found, it should return an empty list. The function should be named `extract_emails`.
  
  assert extract_emails("My email is john@example.com and yours is john@gmail.com.") == ["john@example.com", "john@gmail.com"]
  assert extract_emails("No emails here.") == []
  assert extract_emails("You can contact me at info@company.com or support@company.io.") == ["info@company.com", "support@company.io"]
  assert extract_emails("") == []
output: import re
  
  def extract_emails(text):
      pattern = r'\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b'
      return re.findall(pattern, text)