input: Write a python function to check server load and send an email if it exceeds a threshold.
  assert check_server_load(0.5)==None
  assert check_server_load(0.9)!=None
  assert check_server_load(1.0)!=None
output: import smtplib
  from email.mime.text import MIMEText
  
  def check_server_load(load, threshold=0.8, email='admin@example.com'):
      if load > threshold:
          msg = MIMEText(f'Server load is high: {load}')
          msg['Subject'] = 'High Server Load Alert'
          msg['From'] = 'monitoring@example.com'
          msg['To'] = email
  
          try:
              with smtplib.SMTP('localhost') as server:
                  server.sendmail(msg['From'], [msg['To']], msg.as_string())
              return True
          except Exception as e:
              return str(e)
      return None