If the bird on the left is facing right and the bird on the right is facing left.
return birds ;return #1 that is on the  left  ;return if  #2 is facing right  ;return #1 that is on the  right  ;return if  #4 is facing left  ;return if  both  #3 and #5 are true
['select', 'filter', 'boolean', 'filter', 'boolean', 'boolean']