Add limit check to add_event

[kohlerca]

When using the add_event function to add events to one or more plots (e.g., the output of rasterplot_rates), if the Axes limits were changed and the Event object includes events out of the boundaries, they will be plotted regardless, leading to an unpleasant visualization in notebooks (saving the figure to a file seems to work).

import quantities as pq
from elephant.spike_train_generation import StationaryPoissonProcess
from viziphant.rasterplot import rasterplot_rates
from viziphant.events import add_event
import matplotlib.pyplot as plt
import neo

spiketrains = StationaryPoissonProcess(rate=20 * pq.Hz, t_stop= 2 * pq.s).generate_n_spiketrains(20)

event = neo.Event([0.25, 1, 1.75], units=pq.s, labels=['event_1', 'event_2', 'event_3'])

fig, ax = plt.subplots(figsize=(20,15))
ax = rasterplot_rates(spiketrains, ax=ax)
ax[0].set_xlim([0, 0.75])
ax[1].set_xlim([0, 0.75])
add_event([ax[1], ax[0]], event)

This PR fixes this by adding boundary checks (with respect to the last Axes in the list passed as the function axes parameter).

[Moritz-Alexander-Kern]

Thanks for this enhancement !