input: from typing import Union
  
  def convert_sign(x: Union[int, float]) -> Union[int, float]:
      """ Converts a given integer or float to its opposite sign using bitwise NOT operator.
      If the input is positive, it converts it to negative, and if the input is negative, 
      it converts it to positive.
      >>> convert_sign(5)
      -5
      >>> convert_sign(-3)
      3
      >>> convert_sign(0.75)
      -0.75
      >>> convert_sign(-2.5)
      2.5
      """
      if x > 0:
          return ~int(x) + 1
      elif x < 0:
          return -(~int(-x) + 1)
      else:
          return x
output:     if isinstance(x, float):
          return -x if x > 0 else -x