text: ## StringPart
  
  ```
  StringPart(str, pos)
  ```
  
  > return the character at position `pos` from the `str` string expression.
  
  
  ```
  StringPart(str, {pos1, pos2, pos3,....})
  ```
  
  > return the characters at the position in the list `{pos1, pos2, pos3,....}` from the `str` string expression.
  
  ### Examples
  
  ```
  >> StringPart("1234567890",  {1, 3, 10}) 
  {1,3,0}
  ```
  