input: Write a function that formats a given piece of text with different options for font-style, size, and color. The function should return the text wrapped in an HTML span element with the specified styles. If the input text is empty, the function should return an empty string.
  
  def format_text(text, font="Times New Roman", size='14px', color='#000000'):
      if text == "":
          return ""
      return "<span style='font-family: {}; font-size: {}; color: {};'>{}</span>".format(font, size, color, text)
  
  assert format_text('Lorem ipsum dolor sit amet, consectetur adipiscing elit.') == "<span style='font-family: Times New Roman; font-size: 14px; color: #000000;'>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</span>"
  assert format_text('', 'Arial', '12px', '#FF0000') == ""
  assert format_text('Aliquam non velit sit amet arcu placerat vulputate a ut nibh.', 'Courier New', '16px', '#00FF00') == "<span style='font-family: Courier New; font-size: 16px; color: #00FF00;'>Aliquam non velit sit amet arcu placerat vulputate a ut nibh.</span>"
output: def format_text(text, font="Times New Roman", size='14px', color='#000000'):
      if text == "":
          return ""
      return "<span style='font-family: {}; font-size: {}; color: {};'>{}</span>".format(font, size, color, text)