<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_ve_base(self, environ):
 """Find a directory to look for virtualenvs in. """

        # set ve_base to a path we can look for virtualenvs:
        # 1. .vexrc
        # 2. WORKON_HOME (as defined for virtualenvwrapper's benefit)
        # 3. $HOME/.virtualenvs
        # (unless we got --path, then we don't need it)
        ve_base_value = self.headings[self.default_heading].get('virtualenvs')
        if ve_base_value:
            ve_base = os.path.expanduser(ve_base_value)
        else:
            ve_base = environ.get('WORKON_HOME', '')
        if not ve_base:
            # On Cygwin os.name == 'posix' and we want $HOME.
            if platform.system() == 'Windows' and os.name == 'nt':
                _win_drive = environ.get('HOMEDRIVE')
                home = environ.get('HOMEPATH', '')
                if home:
                    home = os.path.join(_win_drive, home)
            else:
                home = environ.get('HOME', '')
            if not home:
                home = os.path.expanduser('~')
            if not home:
                return ''
            ve_base = os.path.join(home, '.virtualenvs')
        # pass through invalid paths so messages can be generated
        # if not os.path.exists(ve_base) or os.path.isfile(ve_base):
            # return ''
        return ve_base or ''