'Return a string in key=value&key=value form.
Values of None are not included in the output string.
Args:
parameters (dict): dictionary of query parameters to be converted into a
string for encoding and sending to Twitter.
Returns:
A URL-encoded string in "key=value&key=value" form'

def _EncodeParameters(self, parameters):

    if (parameters is None):
        return None
    if (not isinstance(parameters, dict)):
        raise TwitterError('`parameters`    must    be    a    dict.')
    else:
        return urlencode(dict(((k, v) for (k, v) in parameters.items() if (v is not None))))
