class_docstr: Calculates a commission for a transaction based on a per trade cost.
  
  Parameters
  ----------
  cost : float, optional
      The flat amount of commissions paid per equity trade.
class_docstr_tok: ["Calculates","a","commission","for","a","transaction","based","on","a","per","trade","cost",".","Parameters","--","--","--","--","--","cost",":","float",",","optional","The","flat","amount","of","commissions","paid","per","equity","trade","."]
docstr: Cost parameter is the cost of a trade, regardless of share count.
  $5.00 per trade is fairly typical of discount brokers.
docstr_tok: ["Cost","parameter","is","the","cost","of","a","trade",",","regardless","of","share","count",".","$","5.00","per","trade","is","fairly","typical","of","discount","brokers","."]
code: def __init__(self, cost=DEFAULT_MINIMUM_COST_PER_EQUITY_TRADE):
      """
      Cost parameter is the cost of a trade, regardless of share count.
      $5.00 per trade is fairly typical of discount brokers.
      """
      # Cost needs to be floating point so that calculation using division
      # logic does not floor to an integer.
      self.cost = float(cost)
  
imports: from abc import abstractmethod
  from collections import defaultdict
  from six import with_metaclass
  from toolz import merge
  from catalyst.assets import Equity, Future
  from catalyst.finance.constants import FUTURE_EXCHANGE_FEES_BY_SYMBOL
  from catalyst.finance.shared import AllowedAssetMarker, FinancialModelMeta
  from catalyst.utils.dummy import DummyMapping
label_desc: Use image node_id 1 to create a new PerTrade object from inherited base classes: CommissionModel with example: obj = PerTrade(cost)