'Instantiate a new twitter.Api object.
Args:
username: The username of the twitter account.  [optional]
password: The password for the twitter account. [optional]
input_encoding: The encoding used to encode input strings. [optional]
request_header: A dictionary of additional HTTP request headers. [optional]'

def __init__(self, username=None, password=None, input_encoding=None, request_headers=None):

    self._cache = _MemCache()
    self._urllib = urllib2
    self._cache_timeout = Api.DEFAULT_CACHE_TIMEOUT
    self._InitializeRequestHeaders(request_headers)
    self._InitializeUserAgent()
    self._InitializeDefaultParameters()
    self._input_encoding = input_encoding
    self.SetCredentials(username, password)
