code: def bc_gas(self, ya, yb):
      return np.array([ya[0] - 1, yb[0]])
  
imports: import numpy
  from .common import Benchmark, safe_import
  from scipy.integrate import quad, cumulative_simpson
label_desc: Use image node_id 8 for calling the SolveBVP obj's underlying member method code with example usage: obj.bc_gas(ya, yb) and returns: np