code: func validatePSPCapsAgainstDrops(requiredDrops []core.Capability, capsToCheck []core.Capability, fldPath *field.Path) field.ErrorList {
  	allErrs := field.ErrorList{}
  	if requiredDrops == nil {
  		return allErrs
  	}
  	for _, cap := range capsToCheck {
  		if hasCap(cap, requiredDrops) {
  			allErrs = append(allErrs, field.Invalid(fldPath, cap,
  				fmt.Sprintf("capability is listed in %s and requiredDropCapabilities", fldPath.String())))
  		}
  	}
  	return allErrs
  }
docs: // validatePSPCapsAgainstDrops ensures an allowed cap is not listed in the required drops.