<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def load_file_to_base64_str(f_path):
 """Loads the content of a file into a base64 string. Args: f_path: full path to the file including the file name. Returns: A base64 string representing the content of the file in utf-8 encoding. """

    path = abs_path(f_path)
    with io.open(path, 'rb') as f:
        f_bytes = f.read()
        base64_str = base64.b64encode(f_bytes).decode("utf-8")
        return base64_str