def infinitve(conjugate, infinitive_map):
    """Get infinitive form of a conjugated verb.

    Given a mapping of conjugate to infinitive, this function computes
    the infinitive form of a conjugate verb. We provide models available
    for downloading, so you do not have to worry about the ``infinitive_map``.
    Regretfully we only provide models for Spanish texts.

    :param conjugate: Verb to be processed
    :type conjugate: string
    :param infinitve_map: Lexicon containing maps from conjugate to infinitive.
    :type infinitive_map: dict
    :return: Infinitive form of the verb, None if not found
    :rtype: string
    """
    conjugate = conjugate.lower()
    for word_list in infinitive_map:
        if conjugate in word_list:
            infinitive = infinitive_map[word_list]
            return infinitive if infinitive else None
    return None
