parameters: (self, iban)
return_statement: return None
docstring: Reads a swiss postal account number from a an IBAN and returns it as
          a string. Returns None if no valid postal account number was found, or
          the given iban was not from Swiss Postfinance.
  
          CH09 0900 0000 1000 8060 7 -> 10-8060-7
docstring_summary: Reads a swiss postal account number from a an IBAN and returns it as
          a string. Returns None if no valid postal account number was found, or
          the given iban was not from Swiss Postfinance.
docstring_tokens: Reads a swiss postal account number from a an IBAN and returns it as a string . Returns None if no valid postal account number was found or the given iban was not from Swiss Postfinance .
function: def _retrieve_l10n_ch_postal(self, iban):
          """Reads a swiss postal account number from a an IBAN and returns it as
          a string. Returns None if no valid postal account number was found, or
          the given iban was not from Swiss Postfinance.
  
          CH09 0900 0000 1000 8060 7 -> 10-8060-7
          """
          if self._is_postfinance_iban(iban):
              # the IBAN corresponds to a swiss account
              return self._pretty_postal_num(iban[-9:])
          return None
function_tokens: def _retrieve_l10n_ch_postal ( self , iban ) : if self . _is_postfinance_iban ( iban ) : # the IBAN corresponds to a swiss account return self . _pretty_postal_num ( iban [ - 9 : ] ) return None