Avoid recursive repr issues

[jbednar]

Addresses #209 and #396 to avoid infinite recursion when printing a Parameterized object that contains an indirect reference to itself.

First tried using reprlib.recursive_repr, which seemed to work for repr itself, but did not address pprint, because it did not allow the decorated method to have any extra arguments. Luckily the implementation is straightforward, so I copied it from https://github.com/python/cpython/blob/3.2/Lib/reprlib.py and changed it to handle args and kwargs. I did have to change from _thread import get_ident to avoid private API, but it seems the same as from threading import get_ident, which appears to work the same.

I haven't run the test suite yet, but it addresses #209:

import param
class A(param.Parameterized):
    
    b = param.Parameter()
    
class B(param.Parameterized):
    
    a = param.Parameter()
    
a = A()
b = B(a=a)
a.b = b
a.pprint()

'A(b=main.B(a=...))`

and #396:

import param

class InputDataComponent(param.Parameterized):
    update_data = param.Action()
    # download_data = param.Action()

    def __init__(self, **params):
        super().__init__(**params)

        self.update_data = self._update_data
        # self.download_data = self._download_data

    def _update_data(self, event):
        raise NotImplementedError()

    def _download_data(self, event):
        raise NotImplementedError()

repr(InputDataComponent())

"InputDataComponent(name='InputDataComponent00004', update_data=<bound method InputDataComponent._update_data of ...>)"

[philippjfr]

Finally! Thanks for tackling this one.

[philippjfr]

Looks good, and nice solution.