input: Write a function to format a given piece of text with different options for font-style, size, and color. The function should return the formatted text as a HTML span element with inline CSS styles. If no options are provided, the function should use default values for font ("Times New Roman"), size ("14px"), and color ("#000000").
  def format_text(text, font="Times New Roman", size='14px', color='#000000'):
    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('Aliquam non velit sit amet arcu placerat vulputate a ut nibh.', 'Arial', '16px', '#FF0000')=='<span style=\'font-family: Arial font-size: 16px color: #FF0000\'>Aliquam non velit sit amet arcu placerat vulputate a ut nibh.</span>'
  assert format_text('')=='<span style=\'font-family: Times New Roman font-size: 14px color: #000000\'></span>'
  assert format_text('Integer ut lectus vel nisi consequat bibendum ac a erat.')=='<span style=\'font-family: Times New Roman font-size: 14px color: #000000\'>Integer ut lectus vel nisi consequat bibendum ac a erat.</span>'
  assert format_text('arcu placerat vulputate', 'Verdana', '20px')=='<span style=\'font-family: Verdana font-size: 20px color: #000000\'>arcu placerat vulputate</span>'
output: def format_text(text, font="Times New Roman", size='14px', color='#000000'):
    return "<span style='font-family: {}; font-size: {}; color: {};'>{}</span>".format(font, size, color, text)