input: Write a python function to extract floating-point numbers from a string using regular expressions.
  assert extract_floats("The values are 23.4, 45.6, and 78.9.") == [23.4, 45.6, 78.9]
  assert extract_floats("Numbers in scientific notation: 1.23e4, 5.67E-3") == [1.23e4, 5.67e-3]
  assert extract_floats("No numbers here!") == []
output: import re
  
  def extract_floats(s):
      pattern = r'[-+]?\d*\.\d+([eE][-+]?\d+)?'
      return [float(num) for num in re.findall(pattern, s)]