text: """
  Name: Bondi
  References: Bondi, Proc. Roy. Soc. Lond. A, v282, p303, (1964)
  Coordinates: Spherical
  Symmetry: Spherical
  Notes: Ingoing Coordinates
  """
  from sympy import Function, diag, sin, symbols
  
  coords = symbols("r v theta phi", real=True)
  variables = ()
  functions = symbols("C M", cls=Function)
  r, v, th, ph = coords
  C, M = functions
  metric = diag(0, -C(r, v) ** 2 * (1 - 2 * M(r, v) / r), r ** 2, r ** 2 * sin(th) ** 2)
  metric[0, 1] = metric[1, 0] = C(r, v)
  