parameters: (self)
docstring: The node immediately preceding the invocant in their parent's children
          list. If the invocant does not have a previous sibling, it is None.
docstring_summary: The node immediately preceding the invocant in their parent's children
          list. If the invocant does not have a previous sibling, it is None.
docstring_tokens: The node immediately preceding the invocant in their parent s children list . If the invocant does not have a previous sibling it is None .
function: def prev_sibling(self):
          """
          The node immediately preceding the invocant in their parent's children
          list. If the invocant does not have a previous sibling, it is None.
          """
          if self.parent is None:
              return None
  
          # Can't use index(); we need to test by identity
          for i, child in enumerate(self.parent.children):
              if child is self:
                  if i == 0:
                      return None
                  return self.parent.children[i-1]
function_tokens: def prev_sibling ( self ) : if self . parent is None : return None # Can't use index(); we need to test by identity for i , child in enumerate ( self . parent . children ) : if child is self : if i == 0 : return None return self . parent . children [ i - 1 ]