There's a Python code snippet:

def search$($graph$,$ root$)$:

sequence $=[$ root $]$

visited $=$set$()$

while sequence:

node $=$ sequence. pop$()$

if node not in visited:

visited.add$($node$)$

sequence.extend$($graph$[$node$])$

return visited

Which searching algorithm the above code uses and what data structure it employs $(5$ pts$)?$