input: Write a function to extract all public email addresses from a given string. The function should use regular expressions to find and return a list of email addresses found in the input text. If no email addresses are found, it should return an empty list.
  
  def extract_emails(text):
    emails = re.findall(r"[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+", text)
    return 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("Contact us at support@company.com or info@company.com.")==["support@company.com", "info@company.com"]
  assert extract_emails("This text has no email addresses.")==[]
  assert extract_emails("")==[]
output: import re
  
  def extract_emails(text):
    emails = re.findall(r"[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+", text)
    return emails