text: Title: Add Docstrings 
  Body: ### Is there an existing issue for this?
  
  - [X] I have searched the existing issues
  
  ### Is your feature request related to a problem? Please describe.
  
  Having docstrings for all methods and classes will help new contributors understand the codebase and also provide a method of autogenerated API docs. Right now only some methods and classes have docstrings.
  
  ### Describe the solution you'd like.
  
  Example of already implemented docstring.
  
  ```
  def get_aggs(self,
                   symbol: str,
                   multiplier: int,
                   timespan: str,
                   _from: str,
                   to: str) -> Aggs:
          """
          :param symbol: str eg AAPL
          :param multiplier: must be 1
          :param timespan: day or minute
          :param _from: yyyy-mm-dd
          :param to: yyyy-mm-dd
          :return:
          """
          resp = self.data_get('/aggs/ticker/{}/range/{}/{}/{}/{}'.format(
              symbol, multiplier, timespan, _from, to
          ))
          return self.response_wrapper(resp, Aggs)
  ```
  
  ### Describe an alternate solution.
  
  _No response_
  
  ### Anything else? (Additional Context)
  
  _No response_