code: def previousElementSibling(self):
          '''
              previousElementSibling - Returns the previous  sibling  that is an element. 
  
                                          This is the previous tag node in the parent's list of children
  
  
                  @return <None/AdvancedTag> - None if there are no children (tag) in the parent before this node,
                                                      Otherwise the previous element (tag)
  
          '''
          parentNode = self.parentNode
  
          # If no parent, no siblings
          if not parentNode:
              return None
  
          # Determine this node's index in the children of parent
          myElementIdx = parentNode.children.index(self)
          
          # If we are the first child, no previous element
          if myElementIdx == 0:
              return None
  
          # Else, return previous element tag
          return parentNode.children[myElementIdx-1f previousElementSibling(self):
          '''
              previousElementSibling - Returns the previous  sibling  that is an element. 
  
                                          This is the previous tag node in the parent's list of children
  
  
                  @return <None/AdvancedTag> - None if there are no children (tag) in the parent before this node,
                                                      Otherwise the previous element (tag)
  
          '''
          parentNode = self.parentNode
  
          # If no parent, no siblings
          if not parentNode:
              return None
  
          # Determine this node's index in the children of parent
          myElementIdx = parentNode.children.index(self)
          
          # If we are the first child, no previous element
          if myElementIdx == 0:
              return None
  
          # Else, return previous element tag
          return parentNode.children[myElementIdx-1]
docs: previousElementSibling - Returns the previous  sibling  that is an element. 
  
                                          This is the previous tag node in the parent's list of children
  
  
                  @return <None/AdvancedTag> - None if there are no children (tag) in the parent before this node,
                                                      Otherwise the previous element (tag)