<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def long_to_hex(l, size):
 """Encode a long value as a hex string, 0-padding to size. Note that size is the size of the resulting hex string. So, for a 32Byte long size should be 64 (two hex characters per byte"."""

    f_str = "{0:0%sx}" % size
    return ensure_bytes(f_str.format(l).lower())