<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_to_path(p):
 """Adds a given path to the PATH."""

    if p not in os.environ["PATH"]:
        os.environ["PATH"] = "{0}{1}{2}".format(p, os.pathsep, os.environ["PATH"])