load blob content from file in StorageBlobModel instance. Parameters are:
        - path_to_file (required): path to a local file 
        - mimetype (optional): set a mimetype. azurestoragewrap will guess it if not given

def fromfile(self, path_to_file, mimetype=None):
        """ 
        load blob content from file in StorageBlobModel instance. Parameters are:
        - path_to_file (required): path to a local file 
        - mimetype (optional): set a mimetype. azurestoragewrap will guess it if not given 
        """

        if os.path.isfile(path_to_file):

            # Load file into self.__content__
            self.filename = os.path.basename(path_to_file)
            with open(path_to_file, "rb") as in_file:
                self.content = in_file.read()

            #guess mime-type
            self.properties.content_settings = ContentSettings()
            
            if mimetype is None:
                mimetype = guess_type(path_to_file)
                if mimetype[0] is None:
                    mimetype = 'application/octet-stream'
                else: 
                    if not mimetype[1] is None:
                        self.properties.content_settings.content_encoding = mimetype[1]
                    mimetype = mimetype[0]

            self.properties.content_settings.content_type = mimetype

        else:
            raise AzureStorageWrapException(self, 'Can not load blob content, because given path is not a local file')