function trimLeft(string, chars, guards) {
      string = string == null ? '' : String(string);
      if (!string) {
        return string;
      }
      if (guards || chars == null) {
        return string.slice(trimmedLeftIndex(string))
      }
      chars = String(chars);
      return string.slice(charsLeftIndex(string, chars));
    }
Removes leading whitespace or specified characters from `string`.

@static
@memberOf _
@category String
@param {string} [string=''] The string to trim.
@param {string} [chars=whitespace] The characters to trim.
@param- {Object} [guard] Enables use as a callback for functions like `_.map`.
@returns {string} Returns the trimmed string.
@example

_.trimLeft('  fred  ');
// => 'fred  '

_.trimLeft('-_-fred-_-', '_-');
// => 'fred-_-'