input: Write a function to format a given piece of text (input) with different options for font-style, size, and color. The function should return the formatted text as an HTML-encoded span element. If no options are provided, default values for font-style, size, and color should be used.
  
  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('Text Example')=='<span style='font-family: Times New Roman font-size: 14px color: #000000'>Text Example</span>'
  assert format_text('Text Example', font='Arial', size='12px', color='#ff0000')=='<span style='font-family: Arial font-size: 12px color: #ff0000'>Text Example</span>'
  assert format_text() == "<span style='font-family: Times New Roman font-size: 14px color: #000000'></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)