new_contents: """
  The ideal gas law, also called the general gas equation, is the
  equation of state of a hypothetical ideal gas. It is a good approximation
  of the behavior of many gases under many conditions, although it has
  several limitations. It was first stated by Benoît Paul Émile Clapeyron
  in 1834 as a combination of the empirical Boyle's law, Charles's law,
  Avogadro's law, and Gay-Lussac's law.[1] The ideal gas law is often written
  in an empirical form:
   ------------
   | PV = nRT |
   ------------
  P	=	Pressure (Pa)
  V	=	Volume (m^3)
  n	=	Amount of substance (mol)
  R	=	Universal gas constant
  T	=	Absolute temperature (Kelvin)
  
  (Description adapted from https://en.wikipedia.org/wiki/Ideal_gas_law )
  """
  
  UNIVERSAL_GAS_CONSTANT = 8.314462  # Unit - J mol-1 K-1
  
  
  def pressure_of_gas_system(moles: float, kelvin: float, volume: float) -> float:
      """
      >>> pressure_of_gas_system(2, 100, 5)
      332.57848
      >>> pressure_of_gas_system(0.5, 273, 0.004)
      283731.01575
      >>> pressure_of_gas_system(3, -0.46, 23.5)
      Traceback (most recent call last):
          ...
      ValueError: Invalid inputs. Enter positive value.
      """
      if moles < 0 or kelvin < 0 or volume < 0:
          raise ValueError("Invalid inputs. Enter positive value.")
      return moles * kelvin * UNIVERSAL_GAS_CONSTANT / volume
  
  
  def volume_of_gas_system(moles: float, kelvin: float, pressure: float) -> float:
      """
      >>> volume_of_gas_system(2, 100, 5)
      332.57848
      >>> volume_of_gas_system(0.5, 273, 0.004)
      283731.01575
      >>> volume_of_gas_system(3, -0.46, 23.5)
      Traceback (most recent call last):
          ...
      ValueError: Invalid inputs. Enter positive value.
      """
      if moles < 0 or kelvin < 0 or pressure < 0:
          raise ValueError("Invalid inputs. Enter positive value.")
      return moles * kelvin * UNIVERSAL_GAS_CONSTANT / pressure
  
  
  if __name__ == "__main__":
      from doctest import testmod
  
      testmod()
  
subject: Add Ideal Gas Law for physics (#6503)