function baseCreateCallback(func, thisArg, argCount) {
      if (typeof func != 'function') {
        return identity;
      }
      // exit early for no `thisArg` or already bound by `Function#bind`
      if (typeof thisArg == 'undefined' || !('prototype' in func)) {
        return func;
      }
      var bindData = func.__bindData__;
      if (typeof bindData == 'undefined') {
        if (support.funcNames) {
          bindData = !func.name;
        }
        bindData = bindData || !support.funcDecomp;
        if (!bindData) {
          var source = fnToString.call(func);
          if (!support.funcNames) {
            bindData = !reFuncName.test(source);
          }
          if (!bindData) {
            // checks if `func` references the `this` keyword and stores the result
            bindData = reThis.test(source);
            setBindData(func, bindData);
          }
        }
      }
      // exit early if there are no `this` references or `func` is bound
      if (bindData === false || (bindData !== true && bindData[1] & 1)) {
        return func;
      }
      switch (argCount) {
        case 1: return function(value) {
          return func.call(thisArg, value);
        };
        case 2: return function(a, b) {
          return func.call(thisArg, a, b);
        };
        case 3: return function(value, index, collection) {
          return func.call(thisArg, value, index, collection);
        };
        case 4: return function(accumulator, value, index, collection) {
          return func.call(thisArg, accumulator, value, index, collection);
        };
      }
      return bind(func, thisArg);
    }
The base implementation of `_.createCallback` without support for creating
"_.pluck" or "_.where" style callbacks.

@private
@param {*} [func=identity] The value to convert to a callback.
@param {*} [thisArg] The `this` binding of the created callback.
@param {number} [argCount] The number of arguments the callback accepts.
@returns {Function} Returns a callback function.