function walk_pathway!(ao::AbstractOverlapping,walker::PathwayWalker,pulse_effects::Vector{Symbol},nreadout::Ref{Int},block_start_time=0.::VariableType)
function walk_pathway!(ao::AbstractOverlapping,walker::PathwayWalker,pulse_effects::Vector{Symbol},nreadout::Ref{Int},block_start_time=0.::VariableType)