multimode_density_f: obtain conditional pdf value for y values for "v"...
In benjaminleroy/simulationBands: Conformal Prediction Bands with Simulations

conditional pdf is defined under y ~ p1 M1(x) + p2 M2(x) where (M1,M2)(x) ~ right_intercept + N(right_beta*x, right_sd) and (p1,p2) = right_proportions

multimode_density_f(
  y,
  x_val,
  beta = c(-1, 1),
  intercept = c(0, 0),
  sd = c(1, 1),
  proportions = c(0.5, 0.5)
)

`y`	can be a vector
`x_val`	a single value
`beta`	vector length 2, see above
`intercept`	vector length 2, see above
`sd`	vector length 2, see above
`proportions`	vector length 2, see above