code: def is_email(potential_email_address):
      
      context, mail = parseaddr(potential_email_address)
      first_condition = len(context) == 0 and len(mail) != 0
      dot_after_at = ('@' in potential_email_address and
                      '.' in potential_email_address.split('@')[1])
      return first_condition and dot_after_at
docs: Check if potential_email_address is a valid e-mail address.
  
      Please note that this function has no false-negatives but many
      false-positives. So if it returns that the input is not a valid
      e-mail adress, it certainly isn't. If it returns True, it might still be
      invalid. For example, the domain could not be registered.
  
      Parameters
      ----------
      potential_email_address : str
  
      Returns
      -------
      is_email : bool
  
      Examples
      --------
      >>> is_email('')
      False
      >>> is_email('info@martin-thoma.de')
      True
      >>> is_email('info@math.martin-thoma.de')
      True
      >>> is_email('Martin Thoma <info@martin-thoma.de>')
      False
      >>> is_email('info@martin-thoma')
      False